diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 92816a9..534aa89 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,13 +16,14 @@ jobs:
       - name: Install uv and nox
         run: pip install uv nox
       - name: Run checks (lint, format, typecheck)
-        run: nox -s check
+        run: nox -s check -P 3.12
 
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
+        # python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
@@ -32,7 +33,7 @@ jobs:
       - name: Install uv and nox
         run: pip install uv nox
       - name: Run tests
-        run: nox -s test -p ${{ matrix.python-version }}
+        run: nox -s tests -p ${{ matrix.python-version }}
 
   build:
     runs-on: ubuntu-latest
diff --git a/CHANGES.md b/CHANGES.md
index 3ce4517..c6d69a7 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -14,18 +14,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - `__enter__()` return value is bound to the `as` variable
   - `__exit__(None, None, None)` called in `finally` block
   - Falls back to `.close()` for objects without context manager methods
+- **Class system enhancements**:
+  - `super()` support with `super_proxy` runtime helper for proper method delegation
+  - `@staticmethod` decorator - methods with no `this` binding
+  - `@classmethod` decorator - methods receiving constructor as first argument
+  - `@property` decorator with full getter/setter/deleter support via `Object.defineProperty()`
+  - Comparison special methods: `__eq__`, `__lt__`, `__gt__`, `__le__`, `__ge__` dispatch
+  - Container special methods: `__getitem__`, `__setitem__`, `__delitem__` dispatch
+  - Runtime helpers: `op_lt`, `op_gt`, `op_le`, `op_ge`, `op_delitem`, `op_delattr`
 
 ### Changed
 
 - **Zero runtime dependencies**: Removed `buildstr`, `plum-dispatch`, and `dukpy`
-  - `buildstr` replaced with simple string operations in list/tuple generation
-  - `plum-dispatch` was never used
-  - `dukpy` dev dependency removed (tests use `quickjs`)
 - **Removed dead code**: `src/prescrypt/namespace.py` (unused, superseded by binder)
+- **Comparison operators**: Now use runtime helpers for non-primitive types to support special methods
 
 ### Statistics
 
-- 2381 tests passing
+- 2385 tests passing
 - Zero runtime dependencies
 
 ## [0.9.1] - 2026-01-19
diff --git a/Makefile b/Makefile
index 9741cd3..318009e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 .PHONY: all develop test lint clean doc format build
-.PHONY: clean clean-build clean-pyc clean-test coverage dist docs install lint lint/flake8
+.PHONY: clean clean-test coverage dist docs install lint lint/flake8
 
 # The package name
 PKG=pywire
@@ -79,6 +79,7 @@ clean: clean-test
 		.pytest_cache .pytest .DS_Store  docs/_build docs/cache docs/tmp \
 		dist build pip-wheel-metadata junit-*.xml htmlcov coverage.xml \
 		.ruff_cache
+	cd demos && make clean
 
 ## Cleanup tests artifacts
 clean-test: ## remove test and coverage artifacts
diff --git a/demos/Makefile b/demos/Makefile
new file mode 100644
index 0000000..b07f88c
--- /dev/null
+++ b/demos/Makefile
@@ -0,0 +1,19 @@
+# Demos Makefile - Build all Prescrypt demos
+
+DEMOS = browser browser-extension data-dashboard edge-worker python-playground simulation validation-library
+
+.PHONY: all clean $(DEMOS)
+
+all: $(DEMOS)
+	@echo "All demos built successfully."
+
+$(DEMOS):
+	@echo "Building $@..."
+	@$(MAKE) -C $@ build
+
+clean:
+	@for demo in $(DEMOS); do \
+		echo "Cleaning $$demo..."; \
+		$(MAKE) -C $$demo clean; \
+	done
+	@echo "All demos cleaned."
diff --git a/demos/README.md b/demos/README.md
new file mode 100644
index 0000000..6fe93e8
--- /dev/null
+++ b/demos/README.md
@@ -0,0 +1,161 @@
+# Prescrypt Demos
+
+Example applications showcasing Python-to-JavaScript transpilation with Prescrypt.
+
+## Quick Start
+
+Each demo follows a consistent structure:
+
+```bash
+cd demos/<demo-name>
+make build   # Compile Python to JavaScript
+make serve   # Start local server (optional)
+```
+
+## Available Demos
+
+| Demo | Description | Key Features |
+|------|-------------|--------------|
+| [python-playground](python-playground/) | Interactive Python learning | Pre-compiled examples, live output |
+| [validation-library](validation-library/) | Shared form validation | Backend/frontend code reuse |
+| [data-dashboard](data-dashboard/) | Sales analytics dashboard | Canvas charts, data aggregation |
+| [simulation](simulation/) | Predator-prey simulation | Lotka-Volterra model, animation |
+| [browser-extension](browser-extension/) | Chrome/Firefox extension | Page analysis, price highlighting |
+| [edge-worker](edge-worker/) | Cloudflare Workers | Bot detection, geo-blocking |
+| [browser](browser/) | Basic browser example | Simple DOM manipulation |
+
+## Demo Summaries
+
+### Python Playground
+
+Interactive environment with runnable Python examples: Fibonacci, factorial, prime numbers, sorting algorithms, classes, comprehensions, and FizzBuzz.
+
+```python
+def fibonacci(n: int) -> list:
+    if n <= 0:
+        return []
+    fib = [0, 1]
+    while len(fib) < n:
+        fib.append(fib[-1] + fib[-2])
+    return fib[:n]
+```
+
+### Validation Library
+
+Share validation logic between Python backend and JavaScript frontend. Includes email validation with typo detection, password strength checking, phone number formatting, and credit card validation (Luhn algorithm).
+
+```python
+class ValidationResult:
+    @staticmethod
+    def ok():
+        return ValidationResult(True, [])
+
+    @staticmethod
+    def error(message: str):
+        return ValidationResult(False, [message])
+```
+
+### Data Dashboard
+
+Sales analytics with KPI cards, bar charts, line charts, and pie charts. All rendering done with Canvas 2D API - no external libraries.
+
+```python
+def group_by(data: list, key: str) -> dict:
+    groups = {}
+    for item in data:
+        k = item[key]
+        if k not in groups:
+            groups[k] = []
+        groups[k].append(item)
+    return groups
+```
+
+### Simulation
+
+Predator-prey population dynamics using the Lotka-Volterra equations. Features real-time animation, parameter controls, and phase space visualization.
+
+```python
+def lotka_volterra_step(prey, predators, params):
+    prey_change = (
+        params.prey_birth_rate * prey
+        - params.predation_rate * prey * predators
+    ) * params.dt
+    # ...
+```
+
+### Browser Extension
+
+Chrome/Firefox extension written in Python. Analyzes web pages: highlights expensive items, estimates reading time, counts internal/external links, and provides text statistics.
+
+```python
+def highlight_prices():
+    for el in js.document.querySelectorAll(".price"):
+        price = parse_price(el.textContent)
+        if price > Config.price_threshold:
+            el.style.backgroundColor = "#fef3c7"
+```
+
+### Edge Worker
+
+Cloudflare Workers edge computing logic. Includes bot detection, geo-blocking, A/B testing, and security header injection.
+
+```python
+def is_bot(user_agent: str) -> bool:
+    ua_lower = user_agent.lower()
+    for pattern in BOT_PATTERNS:
+        if pattern in ua_lower:
+            return True
+    return False
+```
+
+## Common Patterns
+
+### JavaScript FFI
+
+Access browser APIs via `import js`:
+
+```python
+import js
+
+# DOM manipulation
+el = js.document.getElementById("my-id")
+el.textContent = "Hello"
+
+# Canvas
+ctx = canvas.getContext("2d")
+ctx.fillRect(0, 0, 100, 100)
+```
+
+### Event Handlers
+
+Use factory functions to create handlers with closures:
+
+```python
+def make_click_handler(item):
+    def handler(event):
+        process(item)
+    return handler
+
+button.addEventListener("click", make_click_handler(data))
+```
+
+### Classes
+
+Full class support including `@staticmethod`, `@classmethod`, and `@property`:
+
+```python
+class Config:
+    @staticmethod
+    def default():
+        return Config(100, 200)
+
+    @property
+    def total(self):
+        return self.a + self.b
+```
+
+## Requirements
+
+- Python 3.9+
+- Prescrypt (`pip install prescrypt` or `uv sync` in repo root)
+- Modern browser (Chrome, Firefox, Safari, Edge, Brave)
diff --git a/demos/browser-extension/Makefile b/demos/browser-extension/Makefile
new file mode 100644
index 0000000..b3b0acc
--- /dev/null
+++ b/demos/browser-extension/Makefile
@@ -0,0 +1,19 @@
+.PHONY: build package test clean
+
+build:
+	py2js src/content.py -o dist/content.js
+
+package: build
+	@echo "Extension ready to load in browser."
+	@echo ""
+	@echo "Chrome: chrome://extensions → Enable Developer mode → Load unpacked"
+	@echo "Firefox: about:debugging → This Firefox → Load Temporary Add-on"
+
+test: build
+	@echo "Opening test page..."
+	python -m http.server 8004 &
+	@sleep 1
+	open http://localhost:8004/test-page.html || xdg-open http://localhost:8004/test-page.html
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/browser-extension/README.md b/demos/browser-extension/README.md
new file mode 100644
index 0000000..db3321a
--- /dev/null
+++ b/demos/browser-extension/README.md
@@ -0,0 +1,93 @@
+# Browser Extension Demo
+
+Write Chrome/Firefox extensions in Python.
+
+## Use Case
+
+Python developers can create browser extensions without learning JavaScript.
+The extension logic is written in Python and compiled to JS by Prescrypt.
+
+## Features
+
+This demo extension analyzes web pages:
+
+- **Price Highlighting**: Marks items over $100 with yellow background
+- **Reading Time**: Estimates time to read based on word count
+- **Link Analysis**: Counts internal vs external links
+- **Text Statistics**: Paragraphs, headings, sentences, characters
+
+## Project Structure
+
+```
+browser-extension/
+├── manifest.json       # Extension manifest (Chrome/Firefox)
+├── popup.html          # Extension popup UI
+├── src/
+│   └── content.py      # Python content script
+├── dist/
+│   └── content.js      # Compiled JavaScript
+├── icons/              # Extension icons
+└── test-page.html      # Test page with sample content
+```
+
+## Build
+
+```bash
+make build   # Compile Python to JavaScript
+```
+
+## Install in Browser
+
+### Chrome
+
+1. Go to `chrome://extensions`
+2. Enable "Developer mode" (top right)
+3. Click "Load unpacked"
+4. Select this directory
+
+### Firefox
+
+1. Go to `about:debugging`
+2. Click "This Firefox"
+3. Click "Load Temporary Add-on"
+4. Select `manifest.json`
+
+## Test
+
+```bash
+make test   # Opens test page in browser
+```
+
+Or manually open `test-page.html` with the extension loaded.
+
+## Python Highlights
+
+```python
+def parse_price(text: str) -> float:
+    """Extract numeric price from '$99.99' or '€199,00'."""
+    # Handle both US and European formats
+    ...
+
+def highlight_prices():
+    """Find and highlight prices above threshold."""
+    for el in js.document.querySelectorAll(".price"):
+        price = parse_price(el.textContent)
+        if price > Config.price_threshold:
+            el.style.backgroundColor = "#fef3c7"
+            el.style.border = "2px solid #f59e0b"
+```
+
+## Why Prescrypt?
+
+- Write extension logic in familiar Python syntax
+- No need to learn JavaScript/TypeScript
+- Same analysis code can run on backend
+- Tiny output (content script ~15 KB)
+
+## Production Enhancements
+
+- Add options page for configuration
+- Persist settings with `chrome.storage`
+- Add keyboard shortcuts
+- Inject CSS instead of inline styles
+- Add i18n support
diff --git a/demos/browser-extension/icons/icon.svg b/demos/browser-extension/icons/icon.svg
new file mode 100644
index 0000000..98e3d1a
--- /dev/null
+++ b/demos/browser-extension/icons/icon.svg
@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 128 128">
+  <defs>
+    <linearGradient id="bg" x1="0%" y1="0%" x2="100%" y2="100%">
+      <stop offset="0%" style="stop-color:#4f46e5"/>
+      <stop offset="100%" style="stop-color:#7c3aed"/>
+    </linearGradient>
+  </defs>
+  <rect width="128" height="128" rx="24" fill="url(#bg)"/>
+  <text x="64" y="85" font-family="system-ui, sans-serif" font-size="64" font-weight="bold" fill="white" text-anchor="middle">Py</text>
+</svg>
diff --git a/demos/browser-extension/icons/icon128.png b/demos/browser-extension/icons/icon128.png
new file mode 100644
index 0000000..bc98ad1
Binary files /dev/null and b/demos/browser-extension/icons/icon128.png differ
diff --git a/demos/browser-extension/icons/icon16.png b/demos/browser-extension/icons/icon16.png
new file mode 100644
index 0000000..b907547
Binary files /dev/null and b/demos/browser-extension/icons/icon16.png differ
diff --git a/demos/browser-extension/icons/icon48.png b/demos/browser-extension/icons/icon48.png
new file mode 100644
index 0000000..c231146
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diff --git a/demos/browser-extension/manifest.json b/demos/browser-extension/manifest.json
new file mode 100644
index 0000000..125db59
--- /dev/null
+++ b/demos/browser-extension/manifest.json
@@ -0,0 +1,27 @@
+{
+  "manifest_version": 3,
+  "name": "Python Page Analyzer",
+  "version": "1.0.0",
+  "description": "Analyze web pages using Python compiled to JavaScript",
+  "permissions": ["activeTab", "scripting"],
+  "action": {
+    "default_popup": "popup.html",
+    "default_icon": {
+      "16": "icons/icon16.png",
+      "48": "icons/icon48.png",
+      "128": "icons/icon128.png"
+    }
+  },
+  "content_scripts": [
+    {
+      "matches": ["<all_urls>"],
+      "js": ["dist/content.js"],
+      "run_at": "document_idle"
+    }
+  ],
+  "icons": {
+    "16": "icons/icon16.png",
+    "48": "icons/icon48.png",
+    "128": "icons/icon128.png"
+  }
+}
diff --git a/demos/browser-extension/popup.html b/demos/browser-extension/popup.html
new file mode 100644
index 0000000..db6db36
--- /dev/null
+++ b/demos/browser-extension/popup.html
@@ -0,0 +1,167 @@
+<!doctype html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <style>
+            body {
+                font-family: system-ui, sans-serif;
+                width: 300px;
+                padding: 20px;
+                margin: 0;
+                background: #1e293b;
+                color: #e2e8f0;
+            }
+
+            h1 {
+                font-size: 18px;
+                margin: 0 0 15px 0;
+                color: #6366f1;
+                display: flex;
+                align-items: center;
+                gap: 8px;
+            }
+
+            .description {
+                font-size: 13px;
+                color: #94a3b8;
+                line-height: 1.5;
+                margin-bottom: 20px;
+            }
+
+            .feature {
+                display: flex;
+                align-items: center;
+                justify-content: space-between;
+                padding: 10px 0;
+                border-bottom: 1px solid #334155;
+            }
+
+            .feature:last-child {
+                border-bottom: none;
+            }
+
+            .feature-name {
+                font-size: 14px;
+            }
+
+            .feature-desc {
+                font-size: 11px;
+                color: #64748b;
+            }
+
+            .toggle {
+                position: relative;
+                width: 40px;
+                height: 22px;
+            }
+
+            .toggle input {
+                opacity: 0;
+                width: 0;
+                height: 0;
+            }
+
+            .slider {
+                position: absolute;
+                cursor: pointer;
+                top: 0;
+                left: 0;
+                right: 0;
+                bottom: 0;
+                background: #334155;
+                border-radius: 22px;
+                transition: 0.3s;
+            }
+
+            .slider:before {
+                position: absolute;
+                content: "";
+                height: 16px;
+                width: 16px;
+                left: 3px;
+                bottom: 3px;
+                background: white;
+                border-radius: 50%;
+                transition: 0.3s;
+            }
+
+            input:checked + .slider {
+                background: #6366f1;
+            }
+
+            input:checked + .slider:before {
+                transform: translateX(18px);
+            }
+
+            .footer {
+                margin-top: 20px;
+                padding-top: 15px;
+                border-top: 1px solid #334155;
+                font-size: 11px;
+                color: #64748b;
+                text-align: center;
+            }
+
+            .footer a {
+                color: #6366f1;
+                text-decoration: none;
+            }
+        </style>
+    </head>
+    <body>
+        <h1>🐍 Page Analyzer</h1>
+        <p class="description">
+            This extension analyzes web pages using Python code compiled to JavaScript by Prescrypt.
+        </p>
+
+        <div class="features">
+            <div class="feature">
+                <div>
+                    <div class="feature-name">Price Highlighting</div>
+                    <div class="feature-desc">Highlight expensive items</div>
+                </div>
+                <label class="toggle">
+                    <input type="checkbox" checked />
+                    <span class="slider"></span>
+                </label>
+            </div>
+
+            <div class="feature">
+                <div>
+                    <div class="feature-name">Reading Time</div>
+                    <div class="feature-desc">Estimate time to read</div>
+                </div>
+                <label class="toggle">
+                    <input type="checkbox" checked />
+                    <span class="slider"></span>
+                </label>
+            </div>
+
+            <div class="feature">
+                <div>
+                    <div class="feature-name">Link Analysis</div>
+                    <div class="feature-desc">Count internal/external links</div>
+                </div>
+                <label class="toggle">
+                    <input type="checkbox" checked />
+                    <span class="slider"></span>
+                </label>
+            </div>
+
+            <div class="feature">
+                <div>
+                    <div class="feature-name">Text Statistics</div>
+                    <div class="feature-desc">Word and character counts</div>
+                </div>
+                <label class="toggle">
+                    <input type="checkbox" checked />
+                    <span class="slider"></span>
+                </label>
+            </div>
+        </div>
+
+        <div class="footer">
+            Powered by <a href="https://github.com/abilian/prescrypt" target="_blank">Prescrypt</a>
+        </div>
+    </body>
+</html>
diff --git a/demos/browser-extension/src/content.py b/demos/browser-extension/src/content.py
new file mode 100644
index 0000000..0f5c636
--- /dev/null
+++ b/demos/browser-extension/src/content.py
@@ -0,0 +1,266 @@
+"""Browser Extension Content Script
+
+A content script that runs on web pages and enhances them.
+Demonstrates writing browser extension logic in Python.
+
+Features:
+- Price highlighting (marks expensive items)
+- Reading time estimation
+- Link analysis
+- Text statistics
+"""
+import js
+
+
+# ============================================================================
+# Configuration
+# ============================================================================
+
+class Config:
+    """Extension configuration."""
+    price_threshold = 100.0
+    reading_speed = 200
+
+
+# ============================================================================
+# Price Highlighting
+# ============================================================================
+
+def parse_price(text: str) -> float:
+    """Extract numeric price from text like '$99.99'."""
+    cleaned = text.strip()
+
+    for symbol in ["$", "USD"]:
+        cleaned = cleaned.replace(symbol, "")
+
+    cleaned = cleaned.strip()
+
+    if "," in cleaned:
+        cleaned = cleaned.replace(",", "")
+
+    try:
+        return float(cleaned)
+    except ValueError:
+        return -1.0
+
+
+def highlight_prices() -> int:
+    """Find and highlight prices above threshold."""
+    highlighted = 0
+
+    elements = js.document.querySelectorAll(".price")
+    for el in elements:
+        text = el.textContent
+        price = parse_price(text)
+
+        if price > Config.price_threshold:
+            if "prescrypt-highlighted" not in el.className:
+                el.className += " prescrypt-highlighted"
+                el.style.backgroundColor = "#fef3c7"
+                el.style.border = "2px solid #f59e0b"
+                el.style.borderRadius = "4px"
+                el.style.padding = "2px 6px"
+                highlighted += 1
+
+    return highlighted
+
+
+# ============================================================================
+# Reading Time Estimation
+# ============================================================================
+
+def count_words(text: str) -> int:
+    """Count words in text."""
+    words = text.split()
+    return len(words)
+
+
+def estimate_reading_time() -> dict:
+    """Estimate reading time for the page."""
+    main_content = js.document.querySelector("article")
+    if not main_content:
+        main_content = js.document.querySelector("main")
+    if not main_content:
+        main_content = js.document.body
+
+    text = main_content.textContent or ""
+    words = count_words(text)
+    minutes = words / Config.reading_speed
+
+    return {
+        "words": words,
+        "minutes": round(minutes, 1),
+    }
+
+
+# ============================================================================
+# Link Analysis
+# ============================================================================
+
+def analyze_links() -> dict:
+    """Analyze links on the page."""
+    links = js.document.querySelectorAll("a[href]")
+    current_host = js.window.location.hostname
+
+    total = 0
+    external = 0
+    internal = 0
+
+    for link in links:
+        href = link.href
+        total += 1
+
+        if current_host in href:
+            internal += 1
+        else:
+            external += 1
+
+    return {
+        "total": total,
+        "external": external,
+        "internal": internal,
+    }
+
+
+# ============================================================================
+# Text Statistics
+# ============================================================================
+
+def get_text_stats() -> dict:
+    """Get statistics about text on the page."""
+    text = js.document.body.textContent or ""
+
+    chars = len(text)
+    words = count_words(text)
+    sentences = text.count(".") + text.count("!") + text.count("?")
+    paragraphs = len(js.document.querySelectorAll("p"))
+    headings = len(js.document.querySelectorAll("h1, h2, h3, h4, h5, h6"))
+
+    return {
+        "characters": chars,
+        "words": words,
+        "sentences": sentences,
+        "paragraphs": paragraphs,
+        "headings": headings,
+    }
+
+
+# ============================================================================
+# UI Overlay
+# ============================================================================
+
+def create_info_panel():
+    """Create the info panel overlay."""
+    if js.document.getElementById("prescrypt-panel"):
+        return
+
+    panel = js.document.createElement("div")
+    panel.id = "prescrypt-panel"
+
+    # Create header
+    header = js.document.createElement("div")
+    header.className = "prescrypt-header"
+    header.textContent = "Page Analyzer"
+
+    # Create content area
+    content = js.document.createElement("div")
+    content.className = "prescrypt-content"
+    content.id = "prescrypt-content"
+    content.textContent = "Analyzing..."
+
+    panel.appendChild(header)
+    panel.appendChild(content)
+
+    # Apply styles
+    panel.style.position = "fixed"
+    panel.style.top = "20px"
+    panel.style.right = "20px"
+    panel.style.width = "280px"
+    panel.style.background = "#1e293b"
+    panel.style.borderRadius = "12px"
+    panel.style.boxShadow = "0 10px 40px rgba(0,0,0,0.3)"
+    panel.style.fontFamily = "system-ui, sans-serif"
+    panel.style.fontSize = "14px"
+    panel.style.color = "#e2e8f0"
+    panel.style.zIndex = "999999"
+    panel.style.overflow = "hidden"
+
+    header.style.padding = "12px 15px"
+    header.style.background = "#6366f1"
+    header.style.fontWeight = "600"
+
+    content.style.padding = "15px"
+
+    js.document.body.appendChild(panel)
+
+
+def update_panel(data: dict):
+    """Update the panel with analysis results."""
+    content = js.document.getElementById("prescrypt-content")
+    if not content:
+        return
+
+    rt = data["reading_time"]
+    links = data["links"]
+    stats = data["stats"]
+    prices = data["prices_highlighted"]
+
+    # Build content
+    lines = []
+    lines.append("Reading Time: " + str(rt["minutes"]) + " min")
+    lines.append("Words: " + str(rt["words"]))
+    lines.append("")
+    lines.append("Prices highlighted: " + str(prices))
+    lines.append("")
+    lines.append("Links: " + str(links["internal"]) + " internal, " + str(links["external"]) + " external")
+    lines.append("")
+    lines.append("Paragraphs: " + str(stats["paragraphs"]))
+    lines.append("Headings: " + str(stats["headings"]))
+
+    # Clear and rebuild content
+    content.innerHTML = ""
+    for line in lines:
+        p = js.document.createElement("div")
+        p.textContent = line
+        p.style.marginBottom = "5px"
+        if line == "":
+            p.style.height = "10px"
+        content.appendChild(p)
+
+
+# ============================================================================
+# Main Entry Point
+# ============================================================================
+
+def analyze_page():
+    """Run all analyses and show results."""
+    create_info_panel()
+
+    prices_highlighted = highlight_prices()
+    reading_time = estimate_reading_time()
+    links = analyze_links()
+    stats = get_text_stats()
+
+    update_panel({
+        "prices_highlighted": prices_highlighted,
+        "reading_time": reading_time,
+        "links": links,
+        "stats": stats,
+    })
+
+
+def on_load(e):
+    """Handle page load event."""
+    analyze_page()
+
+
+def init():
+    """Initialize the content script."""
+    if js.document.readyState == "complete":
+        analyze_page()
+    else:
+        js.window.addEventListener("load", on_load)
+
+
+# Initialize
+init()
diff --git a/demos/browser-extension/test-page.html b/demos/browser-extension/test-page.html
new file mode 100644
index 0000000..aa23e74
--- /dev/null
+++ b/demos/browser-extension/test-page.html
@@ -0,0 +1,188 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Extension Test Page - Sample E-commerce</title>
+    <style>
+        body {
+            font-family: system-ui, sans-serif;
+            max-width: 1000px;
+            margin: 0 auto;
+            padding: 40px 20px;
+            background: #f8fafc;
+            color: #1e293b;
+            line-height: 1.6;
+        }
+
+        h1 {
+            color: #4f46e5;
+            margin-bottom: 10px;
+        }
+
+        .subtitle {
+            color: #64748b;
+            margin-bottom: 30px;
+        }
+
+        .products {
+            display: grid;
+            grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
+            gap: 20px;
+            margin-bottom: 40px;
+        }
+
+        .product {
+            background: white;
+            border-radius: 12px;
+            padding: 20px;
+            box-shadow: 0 2px 8px rgba(0,0,0,0.1);
+        }
+
+        .product-name {
+            font-weight: 600;
+            margin-bottom: 8px;
+        }
+
+        .price {
+            font-size: 24px;
+            font-weight: 700;
+            color: #10b981;
+        }
+
+        .price.expensive {
+            color: #ef4444;
+        }
+
+        article {
+            background: white;
+            border-radius: 12px;
+            padding: 30px;
+            margin-bottom: 30px;
+        }
+
+        article h2 {
+            color: #1e293b;
+            margin-bottom: 15px;
+        }
+
+        article p {
+            margin-bottom: 15px;
+            color: #475569;
+        }
+
+        .links-section {
+            background: white;
+            border-radius: 12px;
+            padding: 20px;
+        }
+
+        .links-section h3 {
+            margin-bottom: 15px;
+        }
+
+        .links-section ul {
+            display: grid;
+            grid-template-columns: repeat(2, 1fr);
+            gap: 10px;
+        }
+
+        .links-section a {
+            color: #4f46e5;
+        }
+
+        .info-box {
+            background: #eff6ff;
+            border: 1px solid #3b82f6;
+            border-radius: 8px;
+            padding: 15px;
+            margin-bottom: 30px;
+        }
+    </style>
+</head>
+<body>
+    <h1>Sample E-commerce Page</h1>
+    <p class="subtitle">Test page for the Python Page Analyzer extension</p>
+
+    <div class="info-box">
+        <strong>Testing the Extension:</strong>
+        Load the extension in your browser and refresh this page.
+        You should see a floating panel in the top-right corner analyzing this page.
+        Products over $100 will be highlighted in yellow.
+    </div>
+
+    <h2>Featured Products</h2>
+    <div class="products">
+        <div class="product">
+            <div class="product-name">Basic Widget</div>
+            <div class="price">$29.99</div>
+        </div>
+        <div class="product">
+            <div class="product-name">Premium Gadget</div>
+            <div class="price expensive">$149.00</div>
+        </div>
+        <div class="product">
+            <div class="product-name">Standard Tool</div>
+            <div class="price">$59.50</div>
+        </div>
+        <div class="product">
+            <div class="product-name">Deluxe Package</div>
+            <div class="price expensive">$299.99</div>
+        </div>
+        <div class="product">
+            <div class="product-name">Entry Level Kit</div>
+            <div class="price">$45.00</div>
+        </div>
+        <div class="product">
+            <div class="product-name">Professional Suite</div>
+            <div class="price expensive">$599.00</div>
+        </div>
+    </div>
+
+    <article>
+        <h2>About Our Products</h2>
+        <p>
+            Welcome to our sample e-commerce page. This page is designed to test the
+            Python Page Analyzer browser extension built with Prescrypt. The extension
+            demonstrates how you can write browser extension logic entirely in Python
+            and have it compile to efficient JavaScript.
+        </p>
+        <p>
+            The extension analyzes this page in several ways: it estimates reading time
+            based on word count, highlights prices above a threshold, counts internal
+            and external links, and provides text statistics like paragraph and heading
+            counts.
+        </p>
+        <p>
+            All of this analysis is done using Python code that has been transpiled to
+            JavaScript. This means Python developers can write browser extensions without
+            learning JavaScript, while still benefiting from the browser's native
+            performance.
+        </p>
+        <p>
+            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod
+            tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
+            quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
+            consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
+            cillum dolore eu fugiat nulla pariatur.
+        </p>
+    </article>
+
+    <div class="links-section">
+        <h3>Sample Links</h3>
+        <ul>
+            <li><a href="/about">About Us</a></li>
+            <li><a href="/products">All Products</a></li>
+            <li><a href="/contact">Contact</a></li>
+            <li><a href="/faq">FAQ</a></li>
+            <li><a href="https://github.com">GitHub (External)</a></li>
+            <li><a href="https://python.org">Python.org (External)</a></li>
+            <li><a href="https://google.com">Google (External)</a></li>
+            <li><a href="/blog">Blog</a></li>
+        </ul>
+    </div>
+
+    <!-- Include content script for testing without extension installed -->
+    <script src="dist/content.js"></script>
+</body>
+</html>
diff --git a/demos/browser/dist/app.js b/demos/browser/dist/app.js
deleted file mode 100644
index 89f6f91..0000000
--- a/demos/browser/dist/app.js
+++ /dev/null
@@ -1,421 +0,0 @@
-var _pyfunc_create_dict = function () {
-  const d = {};
-  for (let i = 0; i < arguments.length; i += 2) {
-    d[arguments[i]] = arguments[i + 1];
-  }
-  return d;
-};
-var _pyfunc_format = function (v, fmt) {
-  // nargs: 1 2
-  if (fmt === undefined) {
-    return String(v);
-  }
-  fmt = fmt.toLowerCase();
-  let s = String(v);
-  if (fmt.indexOf("!r") >= 0) {
-    try {
-      s = JSON.stringify(v);
-    } catch (e) {
-      s = undefined;
-    }
-    if (typeof s === "undefined") {
-      s = v._IS_COMPONENT ? v.id : String(v);
-    }
-  }
-  let fmt_type = "";
-  if (
-    fmt.slice(-1) == "i" ||
-    fmt.slice(-1) == "f" ||
-    fmt.slice(-1) == "e" ||
-    fmt.slice(-1) == "g"
-  ) {
-    fmt_type = fmt[fmt.length - 1];
-    fmt = fmt.slice(0, fmt.length - 1);
-  }
-  let i0 = fmt.indexOf(":");
-  let i1 = fmt.indexOf(".");
-  let spec1 = "",
-    spec2 = ""; // before and after dot
-  if (i0 >= 0) {
-    if (i1 > i0) {
-      spec1 = fmt.slice(i0 + 1, i1);
-      spec2 = fmt.slice(i1 + 1);
-    } else {
-      spec1 = fmt.slice(i0 + 1);
-    }
-  } else if (i1 >= 0) {
-    // No colon, but has dot (e.g., ".2f" after removing "f")
-    spec1 = fmt.slice(0, i1);
-    spec2 = fmt.slice(i1 + 1);
-  }
-  // Format numbers
-  if (fmt_type == "") {
-  } else if (fmt_type == "i") {
-    // integer formatting, for %i
-    s = parseInt(v).toFixed(0);
-  } else if (fmt_type == "f") {
-    // float formatting
-    v = parseFloat(v);
-    let decimals = spec2 ? Number(spec2) : 6;
-    s = v.toFixed(decimals);
-  } else if (fmt_type == "e") {
-    // exp formatting
-    v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    s = v.toExponential(precision);
-  } else if (fmt_type == "g") {
-    // "general" formatting
-    v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    // Exp or decimal?
-    s = v.toExponential(precision - 1);
-    let s1 = s.slice(0, s.indexOf("e")),
-      s2 = s.slice(s.indexOf("e"));
-    if (s2.length == 3) {
-      s2 = "e" + s2[1] + "0" + s2[2];
-    }
-    let exp = Number(s2.slice(1));
-    if (exp >= -4 && exp < precision) {
-      s1 = v.toPrecision(precision);
-      s2 = "";
-    }
-    // Skip trailing zeros and dot
-    let j = s1.length - 1;
-    while (j > 0 && s1[j] == "0") {
-      j -= 1;
-    }
-    s1 = s1.slice(0, j + 1);
-    if (s1.slice(-1) == ".") {
-      s1 = s1.slice(0, s1.length - 1);
-    }
-    s = s1 + s2;
-  }
-  // prefix/padding
-  let prefix = "";
-  if (spec1) {
-    if (spec1[0] == "+" && v > 0) {
-      prefix = "+";
-      spec1 = spec1.slice(1);
-    } else if (spec1[0] == " " && v > 0) {
-      prefix = " ";
-      spec1 = spec1.slice(1);
-    }
-  }
-  if (spec1 && spec1[0] == "0") {
-    let padding = Number(spec1.slice(1)) - (s.length + prefix.length);
-    s = "0".repeat(Math.max(0, padding)) + s;
-  }
-  return prefix + s;
-};
-var _pyfunc_op_add = function (a, b) {
-  // nargs: 2
-  if (Array.isArray(a) && Array.isArray(b)) {
-    return a.concat(b);
-  }
-  return a + b;
-};
-var _pyfunc_op_equals = function op_equals(a, b) {
-  // nargs: 2
-  let a_type = typeof a;
-  // If a (or b actually) is of type string, number or boolean, we don't need
-  // to do all the other type checking below.
-  if (a_type === "string" || a_type === "boolean" || a_type === "number") {
-    return a == b;
-  }
-
-  if (a == null || b == null) {
-    return a == b;
-  }
-
-  // Check for __eq__ method on either object
-  if (typeof a.__eq__ === 'function') {
-    return a.__eq__(b);
-  }
-  if (typeof b.__eq__ === 'function') {
-    return b.__eq__(a);
-  }
-
-  if (Array.isArray(a) && Array.isArray(b)) {
-    let i = 0,
-      iseq = a.length == b.length;
-    while (iseq && i < a.length) {
-      iseq = op_equals(a[i], b[i]);
-      i += 1;
-    }
-    return iseq;
-  }
-
-  if (a.constructor === Object && b.constructor === Object) {
-    const akeys = Object.keys(a),
-      bkeys = Object.keys(b);
-    akeys.sort();
-    bkeys.sort();
-    let i = 0,
-      iseq = op_equals(akeys, bkeys);
-    while (iseq && i < akeys.length) {
-      const k = akeys[i];
-      iseq = op_equals(a[k], b[k]);
-      i += 1;
-    }
-    return iseq;
-  }
-
-  return a == b;
-};
-var _pyfunc_op_getitem = function op_getitem(obj, key) {
-  // nargs: 2
-  // Python obj[key] - checks for __getitem__ method first
-  if (obj == null) {
-    throw new TypeError("'NoneType' object is not subscriptable");
-  }
-  if (typeof obj.__getitem__ === 'function') {
-    return obj.__getitem__(key);
-  }
-  return obj[key];
-};
-var _pyfunc_op_len = function op_len(obj) {
-  // nargs: 1
-  // Python len() - checks for __len__ method first, then falls back to .length
-  if (obj == null) {
-    throw new TypeError("object of type 'NoneType' has no len()");
-  }
-  if (typeof obj.__len__ === 'function') {
-    return obj.__len__();
-  }
-  if (obj.length !== undefined) {
-    return obj.length;
-  }
-  if (obj.constructor === Object) {
-    return Object.keys(obj).length;
-  }
-  throw new TypeError("object has no len()");
-};
-var _pyfunc_op_setitem = function op_setitem(obj, key, value) {
-  // nargs: 3
-  // Python obj[key] = value - checks for __setitem__ method first
-  if (obj == null) {
-    throw new TypeError("'NoneType' object does not support item assignment");
-  }
-  if (typeof obj.__setitem__ === 'function') {
-    obj.__setitem__(key, value);
-  } else {
-    obj[key] = value;
-  }
-};
-var _pyfunc_truthy = function (v) {
-  if (v === null || typeof v !== "object") {
-    return v;
-  } else if (v.length !== undefined) {
-    return v.length ? v : false;
-  } else if (v.byteLength !== undefined) {
-    return v.byteLength ? v : false;
-  } else if (v.constructor !== Object) {
-    return true;
-  } else {
-    return Object.getOwnPropertyNames(v).length ? v : false;
-  }
-};
-var _pymeth_append = function (x) {
-  // nargs: 1
-  if (!Array.isArray(this)) {
-    return this.append.apply(this, arguments);
-  }
-
-  this.push(x);
-};
-var _pymeth_format = function () {
-  if (this.constructor !== String) return this.format.apply(this, arguments);
-  let parts = [],
-    i = 0,
-    i1,
-    i2;
-  let itemnr = -1;
-  while (i < this.length) {
-    // find opening
-    i1 = this.indexOf("{", i);
-    if (i1 < 0 || i1 == this.length - 1) {
-      break;
-    }
-    if (this[i1 + 1] == "{") {
-      parts.push(this.slice(i, i1 + 1));
-      i = i1 + 2;
-      continue;
-    }
-    // find closing
-    i2 = this.indexOf("}", i1);
-    if (i2 < 0) {
-      break;
-    }
-    // parse
-    itemnr += 1;
-    let fmt = this.slice(i1 + 1, i2);
-    let index = fmt.split(":")[0].split("!")[0];
-    index = index ? Number(index) : itemnr;
-    let s = _pyfunc_format(arguments[index], fmt);
-    parts.push(this.slice(i, i1), s);
-    i = i2 + 1;
-  }
-  parts.push(this.slice(i));
-  return parts.join("");
-};
-var _pymeth_strip = function (chars) {
-  // nargs: 0 1
-  if (this.constructor !== String) return this.strip.apply(this, arguments);
-  chars = chars === undefined ? " \t\r\n" : chars;
-  let i,
-    s1 = this,
-    s2 = "",
-    s3 = "";
-  for (i = 0; i < s1.length; i++) {
-    if (chars.indexOf(s1[i]) < 0) {
-      s2 = s1.slice(i);
-      break;
-    }
-  }
-  for (i = s2.length - 1; i >= 0; i--) {
-    if (chars.indexOf(s2[i]) < 0) {
-      s3 = s2.slice(0, i + 1);
-      break;
-    }
-  }
-  return s3;
-};
-'Todo List Application\n\nA simple interactive todo app demonstrating Prescrypt browser capabilities:\n- DOM manipulation\n- Event handling\n- State management\n';
-
-
-export let todos = [];
-export let next_id = 1;
-
-            export function add_todo(text) {
-            'Add a new todo item.';
-
-/* global next_id */
-
-const todo = _pyfunc_create_dict('id', next_id, 'text', text, 'completed', false);
-_pymeth_append.call(todos, todo);
-
-next_id = _pyfunc_op_add(next_id, 1);
-render();
-
-            }
-
-
-            export function toggle_todo(todo_id) {
-            "Toggle a todo's completed status.";
-
-
-let _pytmp_1_seq = todos;
-if ((typeof _pytmp_1_seq === "object") && (!Array.isArray(_pytmp_1_seq))) { _pytmp_1_seq = Object.keys(_pytmp_1_seq);}
-for (let _pytmp_2_itr = 0; _pytmp_2_itr < _pytmp_1_seq.length; _pytmp_2_itr += 1) {
-    let todo = _pytmp_1_seq[_pytmp_2_itr];
-    if ((_pyfunc_op_equals(_pyfunc_op_getitem(todo, 'id'), todo_id))) {_pyfunc_op_setitem(todo, 'completed', !_pyfunc_truthy(_pyfunc_op_getitem(todo, 'completed')));break;
-
-    }
-}
-render();
-
-            }
-
-
-            export function delete_todo(todo_id) {
-            'Delete a todo item.';
-
-/* global todos */
-
-todos = (function list_comprehension (iter0) {const res = [];if ((typeof iter0 === "object") && !Array.isArray(iter0)) {iter0 = Object.keys(iter0);}for (let i0=0; i0<iter0.length; i0++) {const t = iter0[i0];if (!((!_pyfunc_op_equals(_pyfunc_op_getitem(t, 'id'), todo_id)))) {continue;}{res.push(t);}}return res;}).call(this, todos);
-render();
-
-            }
-
-
-            export function make_toggle_handler(todo_id) {
-            'Create a toggle handler for a specific todo.';
-
-
-let handler = (function handler(e) {
-toggle_todo(todo_id);
-
-}).bind(this);
-
-return handler;
-
-            }
-
-
-            export function make_delete_handler(todo_id) {
-            'Create a delete handler for a specific todo.';
-
-
-let handler = (function handler(e) {
-delete_todo(todo_id);
-
-}).bind(this);
-
-return handler;
-
-            }
-
-
-            export function render() {
-            'Render the todo list to the DOM.';
-
-const container = document.getElementById('todo-list');
-container.innerHTML = '';
-
-let _pytmp_3_seq = todos;
-if ((typeof _pytmp_3_seq === "object") && (!Array.isArray(_pytmp_3_seq))) { _pytmp_3_seq = Object.keys(_pytmp_3_seq);}
-for (let _pytmp_4_itr = 0; _pytmp_4_itr < _pytmp_3_seq.length; _pytmp_4_itr += 1) {
-    let todo = _pytmp_3_seq[_pytmp_4_itr];const item = document.createElement('div');item.className = 'todo-item';
-    if (_pyfunc_truthy(_pyfunc_op_getitem(todo, 'completed'))) {item.className = _pyfunc_op_add(item.className, ' completed');
-    }const checkbox = document.createElement('input');checkbox.type = 'checkbox';checkbox.checked = _pyfunc_op_getitem(todo, 'completed');checkbox.addEventListener('change', make_toggle_handler(_pyfunc_op_getitem(todo, 'id')));
-const span = document.createElement('span');span.textContent = _pyfunc_op_getitem(todo, 'text');const btn = document.createElement('button');btn.textContent = 'Delete';btn.className = 'delete-btn';btn.addEventListener('click', make_delete_handler(_pyfunc_op_getitem(todo, 'id')));
-item.appendChild(checkbox);
-item.appendChild(span);
-item.appendChild(btn);
-container.appendChild(item);
-
-}
-const completed = _pyfunc_op_len(((function list_comprehension (iter0) {const res = [];if ((typeof iter0 === "object") && !Array.isArray(iter0)) {iter0 = Object.keys(iter0);}for (let i0=0; i0<iter0.length; i0++) {const t = iter0[i0];if (!(_pyfunc_op_getitem(t, 'completed'))) {continue;}{res.push(t);}}return res;}).call(this, todos)));
-const total = _pyfunc_op_len(todos);
-document.getElementById('status').textContent = _pymeth_format.call("{}/{} completed", completed, total);
-            }
-
-
-            export function handle_submit(event) {
-            'Handle form submission.';
-
-event.preventDefault();
-
-const input_el = document.getElementById('todo-input');
-const text = _pymeth_strip.call(input_el.value);
-
-if (_pyfunc_truthy(text)) {add_todo(text);
-input_el.value = '';
-}
-            }
-
-
-            export function handle_load(e) {
-            'Handle page load.';
-
-init();
-
-            }
-
-
-            export function init() {
-            'Initialize the application.';
-
-const form = document.getElementById('todo-form');
-form.addEventListener('submit', handle_submit);
-
-add_todo('Learn Prescrypt');
-
-add_todo('Build something cool');
-
-add_todo('Deploy to production');
-
-            }
-
-window.addEventListener('DOMContentLoaded', handle_load);
-//# sourceMappingURL=app.js.map
diff --git a/demos/browser/dist/app.js.map b/demos/browser/dist/app.js.map
deleted file mode 100644
index 540d17d..0000000
--- a/demos/browser/dist/app.js.map
+++ /dev/null
@@ -1 +0,0 @@
-{"version": 3, "file": "app.js", "sources": ["src/app.py"], "mappings": ";;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAA;AAOA,AAGA,AACA,AAGA;;;;;;;;;;;;;AAaA;;;;;;;;;;;;;;;;AASA;;;;;;;;;;AAOA;;;;;;;;;;;;;AAOA;;;;;;;;;;;;;AAOA;;;;;;;;;;;;;;;;;;;;;;;;AAsCA;;;;;;;;;;;;;AAUA;;;;;;;AAKA;;;;;;;;;;;;;;AAYA", "sourcesContent": ["\"\"\"Todo List Application\n\nA simple interactive todo app demonstrating Prescrypt browser capabilities:\n- DOM manipulation\n- Event handling\n- State management\n\"\"\"\nimport js\n\n# Application state\ntodos = []\nnext_id = 1\n\n\ndef add_todo(text):\n    \"\"\"Add a new todo item.\"\"\"\n    global next_id\n    todo = {\n        \"id\": next_id,\n        \"text\": text,\n        \"completed\": False\n    }\n    todos.append(todo)\n    next_id += 1\n    render()\n\n\ndef toggle_todo(todo_id):\n    \"\"\"Toggle a todo's completed status.\"\"\"\n    for todo in todos:\n        if todo[\"id\"] == todo_id:\n            todo[\"completed\"] = not todo[\"completed\"]\n            break\n    render()\n\n\ndef delete_todo(todo_id):\n    \"\"\"Delete a todo item.\"\"\"\n    global todos\n    todos = [t for t in todos if t[\"id\"] != todo_id]\n    render()\n\n\ndef make_toggle_handler(todo_id):\n    \"\"\"Create a toggle handler for a specific todo.\"\"\"\n    def handler(e):\n        toggle_todo(todo_id)\n    return handler\n\n\ndef make_delete_handler(todo_id):\n    \"\"\"Create a delete handler for a specific todo.\"\"\"\n    def handler(e):\n        delete_todo(todo_id)\n    return handler\n\n\ndef render():\n    \"\"\"Render the todo list to the DOM.\"\"\"\n    container = js.document.getElementById(\"todo-list\")\n    container.innerHTML = \"\"\n\n    for todo in todos:\n        item = js.document.createElement(\"div\")\n        item.className = \"todo-item\"\n        if todo[\"completed\"]:\n            item.className += \" completed\"\n\n        # Checkbox\n        checkbox = js.document.createElement(\"input\")\n        checkbox.type = \"checkbox\"\n        checkbox.checked = todo[\"completed\"]\n        checkbox.addEventListener(\"change\", make_toggle_handler(todo[\"id\"]))\n\n        # Text\n        span = js.document.createElement(\"span\")\n        span.textContent = todo[\"text\"]\n\n        # Delete button\n        btn = js.document.createElement(\"button\")\n        btn.textContent = \"Delete\"\n        btn.className = \"delete-btn\"\n        btn.addEventListener(\"click\", make_delete_handler(todo[\"id\"]))\n\n        item.appendChild(checkbox)\n        item.appendChild(span)\n        item.appendChild(btn)\n        container.appendChild(item)\n\n    # Update count\n    completed = len([t for t in todos if t[\"completed\"]])\n    total = len(todos)\n    js.document.getElementById(\"status\").textContent = f\"{completed}/{total} completed\"\n\n\ndef handle_submit(event):\n    \"\"\"Handle form submission.\"\"\"\n    event.preventDefault()\n    input_el = js.document.getElementById(\"todo-input\")\n    text = input_el.value.strip()\n    if text:\n        add_todo(text)\n        input_el.value = \"\"\n\n\ndef handle_load(e):\n    \"\"\"Handle page load.\"\"\"\n    init()\n\n\ndef init():\n    \"\"\"Initialize the application.\"\"\"\n    form = js.document.getElementById(\"todo-form\")\n    form.addEventListener(\"submit\", handle_submit)\n\n    # Add some sample todos\n    add_todo(\"Learn Prescrypt\")\n    add_todo(\"Build something cool\")\n    add_todo(\"Deploy to production\")\n\n\n# Run on page load\njs.window.addEventListener(\"DOMContentLoaded\", handle_load)\n"]}
diff --git a/demos/data-dashboard/Makefile b/demos/data-dashboard/Makefile
new file mode 100644
index 0000000..00f7ad5
--- /dev/null
+++ b/demos/data-dashboard/Makefile
@@ -0,0 +1,10 @@
+.PHONY: build serve clean
+
+build:
+	py2js src/dashboard.py -o dist/dashboard.js -s
+
+serve: build
+	python -m http.server 8003
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/data-dashboard/README.md b/demos/data-dashboard/README.md
new file mode 100644
index 0000000..3c8c930
--- /dev/null
+++ b/demos/data-dashboard/README.md
@@ -0,0 +1,77 @@
+# Data Dashboard Demo
+
+Python data processing and visualization in the browser.
+
+## Use Case
+
+Build **lightweight data dashboards** without heavy dependencies:
+
+- Process CSV/JSON data client-side
+- Interactive charts and filters
+- Statistical calculations
+- Zero server infrastructure needed
+
+## Features
+
+- **KPI Cards**: Total sales, units, averages
+- **Bar Chart**: Sales by region
+- **Pie Chart**: Sales distribution by month
+- **Line Chart**: Monthly trends by region
+- **Data Table**: Top performing entries
+- **Filters**: Filter by region with real-time updates
+
+## Python Data Processing
+
+```python
+def group_by(data: list, key: str) -> dict:
+    """Group data by a key field."""
+    groups = {}
+    for item in data:
+        k = item[key]
+        if k not in groups:
+            groups[k] = []
+        groups[k].append(item)
+    return groups
+
+def calculate_stats(values: list) -> dict:
+    """Calculate basic statistics."""
+    sorted_vals = sorted(values)
+    n = len(sorted_vals)
+    return {
+        "min": sorted_vals[0],
+        "max": sorted_vals[-1],
+        "mean": sum(sorted_vals) / n,
+        "median": sorted_vals[n // 2],
+    }
+```
+
+## Build & Run
+
+```bash
+make build   # Compile Python to JavaScript
+make serve   # Start server on port 8003
+```
+
+Then open http://localhost:8003
+
+## Technical Highlights
+
+- Pure Python data aggregation
+- Canvas 2D chart rendering
+- Dictionary/list comprehensions
+- Statistical calculations
+- DOM manipulation for tables
+
+## Why Not Pandas?
+
+Pandas is 15+ MB and requires NumPy. For simple aggregations and charts,
+Python's built-in data structures are sufficient and compile to tiny JavaScript.
+
+## Extending the Demo
+
+Ideas for enhancement:
+- CSV file upload and parsing
+- Export to PNG/PDF
+- Date range filters
+- Multiple chart types
+- Responsive mobile layout
diff --git a/demos/data-dashboard/index.html b/demos/data-dashboard/index.html
new file mode 100644
index 0000000..8aafe6d
--- /dev/null
+++ b/demos/data-dashboard/index.html
@@ -0,0 +1,286 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Data Dashboard - Prescrypt Demo</title>
+    <style>
+        :root {
+            --bg: #0f172a;
+            --surface: #1e293b;
+            --border: #334155;
+            --text: #e2e8f0;
+            --text-muted: #94a3b8;
+            --accent: #6366f1;
+        }
+
+        * {
+            box-sizing: border-box;
+            margin: 0;
+            padding: 0;
+        }
+
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+            background: var(--bg);
+            color: var(--text);
+            min-height: 100vh;
+        }
+
+        .dashboard {
+            max-width: 1200px;
+            margin: 0 auto;
+            padding: 20px;
+        }
+
+        header {
+            display: flex;
+            justify-content: space-between;
+            align-items: center;
+            margin-bottom: 25px;
+        }
+
+        h1 {
+            font-size: 1.5rem;
+            color: var(--accent);
+        }
+
+        .subtitle {
+            color: var(--text-muted);
+            font-size: 0.9rem;
+        }
+
+        #filters {
+            display: flex;
+            gap: 8px;
+        }
+
+        .filter-btn {
+            padding: 8px 16px;
+            background: var(--surface);
+            border: 1px solid var(--border);
+            border-radius: 6px;
+            color: var(--text-muted);
+            cursor: pointer;
+            font-size: 13px;
+            transition: all 0.2s;
+        }
+
+        .filter-btn:hover {
+            border-color: var(--accent);
+            color: var(--text);
+        }
+
+        .filter-btn.active {
+            background: var(--accent);
+            border-color: var(--accent);
+            color: white;
+        }
+
+        .kpi-grid {
+            display: grid;
+            grid-template-columns: repeat(4, 1fr);
+            gap: 15px;
+            margin-bottom: 25px;
+        }
+
+        .kpi-card {
+            background: var(--surface);
+            border-radius: 10px;
+            padding: 20px;
+        }
+
+        .kpi-label {
+            font-size: 0.8rem;
+            color: var(--text-muted);
+            text-transform: uppercase;
+            letter-spacing: 0.05em;
+        }
+
+        .kpi-value {
+            font-size: 1.8rem;
+            font-weight: 700;
+            color: var(--text);
+            margin-top: 5px;
+        }
+
+        .chart-grid {
+            display: grid;
+            grid-template-columns: 1fr 1fr;
+            gap: 15px;
+            margin-bottom: 25px;
+        }
+
+        .chart-card {
+            background: var(--surface);
+            border-radius: 10px;
+            padding: 15px;
+        }
+
+        .chart-card.wide {
+            grid-column: span 2;
+        }
+
+        canvas {
+            width: 100%;
+            border-radius: 8px;
+        }
+
+        .table-card {
+            background: var(--surface);
+            border-radius: 10px;
+            padding: 20px;
+        }
+
+        .table-header {
+            display: flex;
+            justify-content: space-between;
+            align-items: center;
+            margin-bottom: 15px;
+        }
+
+        .table-title {
+            font-size: 1rem;
+            font-weight: 600;
+        }
+
+        table {
+            width: 100%;
+            border-collapse: collapse;
+        }
+
+        th, td {
+            text-align: left;
+            padding: 12px;
+            border-bottom: 1px solid var(--border);
+        }
+
+        th {
+            font-size: 0.75rem;
+            color: var(--text-muted);
+            text-transform: uppercase;
+            letter-spacing: 0.05em;
+            font-weight: 500;
+        }
+
+        td {
+            font-size: 0.9rem;
+        }
+
+        tr:hover td {
+            background: rgba(99, 102, 241, 0.1);
+        }
+
+        .info-banner {
+            background: rgba(99, 102, 241, 0.1);
+            border: 1px solid var(--accent);
+            border-radius: 8px;
+            padding: 15px 20px;
+            margin-top: 25px;
+            display: flex;
+            align-items: center;
+            gap: 15px;
+        }
+
+        .info-icon {
+            font-size: 24px;
+        }
+
+        .info-text {
+            font-size: 0.9rem;
+            color: var(--text-muted);
+        }
+
+        .info-text strong {
+            color: var(--text);
+        }
+
+        @media (max-width: 900px) {
+            .kpi-grid {
+                grid-template-columns: repeat(2, 1fr);
+            }
+            .chart-grid {
+                grid-template-columns: 1fr;
+            }
+            .chart-card.wide {
+                grid-column: span 1;
+            }
+            header {
+                flex-direction: column;
+                gap: 15px;
+            }
+        }
+    </style>
+</head>
+<body>
+    <div class="dashboard">
+        <header>
+            <div>
+                <h1>📊 Sales Dashboard</h1>
+                <p class="subtitle">Python data processing in the browser</p>
+            </div>
+            <div id="filters"></div>
+        </header>
+
+        <div class="kpi-grid">
+            <div class="kpi-card">
+                <div class="kpi-label">Total Sales</div>
+                <div class="kpi-value" id="kpi-total-sales">$0</div>
+            </div>
+            <div class="kpi-card">
+                <div class="kpi-label">Units Sold</div>
+                <div class="kpi-value" id="kpi-total-units">0</div>
+            </div>
+            <div class="kpi-card">
+                <div class="kpi-label">Avg per Unit</div>
+                <div class="kpi-value" id="kpi-avg-order">$0</div>
+            </div>
+            <div class="kpi-card">
+                <div class="kpi-label">Best Month</div>
+                <div class="kpi-value" id="kpi-best-month">$0</div>
+            </div>
+        </div>
+
+        <div class="chart-grid">
+            <div class="chart-card">
+                <canvas id="chart-region" width="400" height="250"></canvas>
+            </div>
+            <div class="chart-card">
+                <canvas id="chart-month" width="400" height="250"></canvas>
+            </div>
+            <div class="chart-card wide">
+                <canvas id="chart-trend" width="800" height="300"></canvas>
+            </div>
+        </div>
+
+        <div class="table-card">
+            <div class="table-header">
+                <span class="table-title">Top Performing Entries</span>
+            </div>
+            <table>
+                <thead>
+                    <tr>
+                        <th>Region</th>
+                        <th>Month</th>
+                        <th>Sales</th>
+                        <th>Units</th>
+                    </tr>
+                </thead>
+                <tbody id="data-table-body">
+                </tbody>
+            </table>
+        </div>
+
+        <div class="info-banner">
+            <span class="info-icon">🐍</span>
+            <div class="info-text">
+                <strong>100% Python</strong> - Data aggregation, statistics, and chart rendering
+                all written in Python. Click the region filters to see real-time updates.
+                No server required!
+            </div>
+        </div>
+    </div>
+
+    <script type="module" src="dist/dashboard.js"></script>
+</body>
+</html>
diff --git a/demos/data-dashboard/src/dashboard.py b/demos/data-dashboard/src/dashboard.py
new file mode 100644
index 0000000..a1ea391
--- /dev/null
+++ b/demos/data-dashboard/src/dashboard.py
@@ -0,0 +1,484 @@
+"""Data Dashboard Demo
+
+Process and visualize data in the browser using Python.
+Demonstrates Python data processing with interactive charts.
+
+Features:
+- CSV/JSON parsing
+- Data aggregation and grouping
+- Statistical calculations
+- Interactive visualizations
+"""
+from __future__ import annotations
+
+import js
+
+# ============================================================================
+# Sample Data - Sales by Region/Month
+# ============================================================================
+
+SAMPLE_DATA = [
+    {"region": "North", "month": "Jan", "sales": 12500, "units": 150},
+    {"region": "North", "month": "Feb", "sales": 14200, "units": 168},
+    {"region": "North", "month": "Mar", "sales": 13800, "units": 162},
+    {"region": "North", "month": "Apr", "sales": 15600, "units": 185},
+    {"region": "North", "month": "May", "sales": 16800, "units": 198},
+    {"region": "North", "month": "Jun", "sales": 18200, "units": 215},
+    {"region": "South", "month": "Jan", "sales": 9800, "units": 112},
+    {"region": "South", "month": "Feb", "sales": 11200, "units": 128},
+    {"region": "South", "month": "Mar", "sales": 10500, "units": 120},
+    {"region": "South", "month": "Apr", "sales": 12800, "units": 145},
+    {"region": "South", "month": "May", "sales": 14200, "units": 162},
+    {"region": "South", "month": "Jun", "sales": 15800, "units": 180},
+    {"region": "East", "month": "Jan", "sales": 8500, "units": 95},
+    {"region": "East", "month": "Feb", "sales": 9200, "units": 102},
+    {"region": "East", "month": "Mar", "sales": 10100, "units": 115},
+    {"region": "East", "month": "Apr", "sales": 11500, "units": 130},
+    {"region": "East", "month": "May", "sales": 12800, "units": 145},
+    {"region": "East", "month": "Jun", "sales": 14200, "units": 162},
+    {"region": "West", "month": "Jan", "sales": 11200, "units": 125},
+    {"region": "West", "month": "Feb", "sales": 12500, "units": 140},
+    {"region": "West", "month": "Mar", "sales": 11800, "units": 132},
+    {"region": "West", "month": "Apr", "sales": 13200, "units": 148},
+    {"region": "West", "month": "May", "sales": 14800, "units": 165},
+    {"region": "West", "month": "Jun", "sales": 16500, "units": 185},
+]
+
+
+# ============================================================================
+# Data Processing Functions
+# ============================================================================
+
+def group_by(data: list, key: str) -> dict:
+    """Group data by a key field."""
+    groups = {}
+    for item in data:
+        k = item[key]
+        if k not in groups:
+            groups[k] = []
+        groups[k].append(item)
+    return groups
+
+
+def sum_by(data: list, value_key: str) -> float:
+    """Sum values in a list of dicts."""
+    total = 0
+    for item in data:
+        total += item[value_key]
+    return total
+
+
+def avg_by(data: list, value_key: str) -> float:
+    """Average values in a list of dicts."""
+    if not data:
+        return 0
+    return sum_by(data, value_key) / len(data)
+
+
+def calculate_stats(values: list) -> dict:
+    """Calculate basic statistics."""
+    if not values:
+        return {"min": 0, "max": 0, "mean": 0, "median": 0}
+
+    sorted_vals = sorted(values)
+    n = len(sorted_vals)
+
+    return {
+        "min": sorted_vals[0],
+        "max": sorted_vals[-1],
+        "mean": sum(sorted_vals) / n,
+        "median": sorted_vals[n // 2] if n % 2 else (sorted_vals[n//2 - 1] + sorted_vals[n//2]) / 2,
+        "count": n,
+        "sum": sum(sorted_vals),
+    }
+
+
+def get_sales_by_region(data: list) -> dict:
+    """Aggregate sales by region."""
+    by_region = group_by(data, "region")
+    result = {}
+    for region in by_region:
+        result[region] = sum_by(by_region[region], "sales")
+    return result
+
+
+def get_sales_by_month(data: list) -> dict:
+    """Aggregate sales by month."""
+    by_month = group_by(data, "month")
+    result = {}
+    for month in by_month:
+        result[month] = sum_by(by_month[month], "sales")
+    return result
+
+
+def get_monthly_trend(data: list, region: str = None) -> list:
+    """Get monthly sales trend, optionally filtered by region."""
+    filtered = data
+    if region is not None:
+        filtered = [d for d in data if d["region"] == region]
+    by_month = group_by(filtered, "month")
+
+    months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
+    result = []
+    for m in months:
+        if m in by_month:
+            result.append(sum_by(by_month[m], "sales"))
+        else:
+            result.append(0)
+    return result
+
+
+def get_top_performers(data: list, n: int = 5) -> list:
+    """Get top N entries by sales."""
+    sorted_data = sorted(data, key=lambda x: x["sales"], reverse=True)
+    return sorted_data[:n]
+
+
+# ============================================================================
+# Chart Drawing
+# ============================================================================
+
+def draw_bar_chart(canvas_id: str, data: dict, title: str, color: str = "#6366f1"):
+    """Draw a horizontal bar chart."""
+    canvas = js.document.getElementById(canvas_id)
+    ctx = canvas.getContext("2d")
+
+    width = canvas.width
+    height = canvas.height
+    padding = 60
+
+    # Clear
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, width, height)
+
+    # Title
+    ctx.fillStyle = "#e2e8f0"
+    ctx.font = "bold 14px system-ui"
+    ctx.fillText(title, padding, 25)
+
+    if not data:
+        return
+
+    labels = list(data.keys())
+    values = list(data.values())
+    max_val = max(values) if values else 1
+
+    chart_height = height - padding - 40
+    bar_height = min(30, (chart_height - 10 * len(labels)) / len(labels))
+    gap = 10
+
+    # Draw bars
+    for i in range(len(labels)):
+        bar_label = labels[i]
+        bar_value = values[i]
+        y = padding + i * (bar_height + gap)
+        bar_width = (bar_value / max_val) * (width - padding - 80)
+
+        # Bar
+        ctx.fillStyle = color
+        ctx.fillRect(padding, y, bar_width, bar_height)
+
+        # Label
+        ctx.fillStyle = "#94a3b8"
+        ctx.font = "12px system-ui"
+        ctx.textAlign = "right"
+        ctx.fillText(bar_label, padding - 10, y + bar_height / 2 + 4)
+
+        # Value
+        ctx.fillStyle = "#e2e8f0"
+        ctx.textAlign = "left"
+        ctx.fillText("$" + str(int(bar_value)), padding + bar_width + 10, y + bar_height / 2 + 4)
+
+    ctx.textAlign = "left"
+
+
+def draw_line_chart(canvas_id: str, datasets: dict, title: str):
+    """Draw a line chart with multiple datasets."""
+    canvas = js.document.getElementById(canvas_id)
+    ctx = canvas.getContext("2d")
+
+    width = canvas.width
+    height = canvas.height
+    padding = 60
+
+    # Clear
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, width, height)
+
+    # Title
+    ctx.fillStyle = "#e2e8f0"
+    ctx.font = "bold 14px system-ui"
+    ctx.fillText(title, padding, 25)
+
+    months = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
+
+    # Find max value across all datasets
+    all_values = []
+    for ds_vals in datasets.values():
+        all_values.extend(ds_vals)
+    max_val = max(all_values) if all_values else 1
+
+    chart_width = width - padding - 40
+    chart_height = height - padding - 50
+
+    def x_pos(i):
+        return padding + (i / (len(months) - 1)) * chart_width
+
+    def y_pos(v):
+        return padding + 20 + (1 - v / max_val) * chart_height
+
+    # Draw grid
+    ctx.strokeStyle = "#334155"
+    ctx.lineWidth = 1
+    for grid_i in range(5):
+        grid_y = padding + 20 + (grid_i / 4) * chart_height
+        ctx.beginPath()
+        ctx.moveTo(padding, grid_y)
+        ctx.lineTo(width - 40, grid_y)
+        ctx.stroke()
+
+    # Draw X axis labels
+    ctx.fillStyle = "#94a3b8"
+    ctx.font = "11px system-ui"
+    ctx.textAlign = "center"
+    for i in range(len(months)):
+        ctx.fillText(months[i], x_pos(i), height - 15)
+
+    # Colors for different lines
+    colors = ["#6366f1", "#10b981", "#f59e0b", "#ef4444"]
+
+    # Draw lines
+    labels = list(datasets.keys())
+    for idx in range(len(labels)):
+        label = labels[idx]
+        line_values = datasets[label]
+        color = colors[idx % len(colors)]
+        ctx.strokeStyle = color
+        ctx.lineWidth = 2
+
+        ctx.beginPath()
+        for ln_i in range(len(line_values)):
+            ln_v = line_values[ln_i]
+            ln_x = x_pos(ln_i)
+            ln_y = y_pos(ln_v)
+            if ln_i == 0:
+                ctx.moveTo(ln_x, ln_y)
+            else:
+                ctx.lineTo(ln_x, ln_y)
+        ctx.stroke()
+
+        # Draw points
+        ctx.fillStyle = color
+        for pt_i in range(len(line_values)):
+            pt_v = line_values[pt_i]
+            ctx.beginPath()
+            ctx.arc(x_pos(pt_i), y_pos(pt_v), 4, 0, 6.28)
+            ctx.fill()
+
+    # Legend
+    ctx.font = "11px system-ui"
+    legend_x = width - 100
+    for leg_i in range(len(labels)):
+        leg_color = colors[leg_i % len(colors)]
+        leg_y = 45 + leg_i * 18
+
+        ctx.fillStyle = leg_color
+        ctx.fillRect(legend_x, leg_y - 8, 12, 12)
+
+        ctx.fillStyle = "#e2e8f0"
+        ctx.textAlign = "left"
+        ctx.fillText(labels[leg_i], legend_x + 18, leg_y + 2)
+
+
+def draw_pie_chart(canvas_id: str, data: dict, title: str):
+    """Draw a pie chart."""
+    canvas = js.document.getElementById(canvas_id)
+    ctx = canvas.getContext("2d")
+
+    width = canvas.width
+    height = canvas.height
+
+    # Clear
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, width, height)
+
+    # Title
+    ctx.fillStyle = "#e2e8f0"
+    ctx.font = "bold 14px system-ui"
+    ctx.fillText(title, 20, 25)
+
+    if not data:
+        return
+
+    total = sum(data.values())
+    if total == 0:
+        return
+
+    colors = ["#6366f1", "#10b981", "#f59e0b", "#ef4444", "#8b5cf6", "#ec4899"]
+
+    center_x = width // 2
+    center_y = height // 2 + 10
+    radius = min(width, height) // 2 - 60
+
+    start_angle = -3.14159 / 2  # Start at top
+
+    labels = list(data.keys())
+    for idx in range(len(labels)):
+        label = labels[idx]
+        value = data[label]
+        pct = value / total
+        end_angle = start_angle + pct * 2 * 3.14159
+
+        # Draw slice
+        ctx.fillStyle = colors[idx % len(colors)]
+        ctx.beginPath()
+        ctx.moveTo(center_x, center_y)
+        ctx.arc(center_x, center_y, radius, start_angle, end_angle)
+        ctx.closePath()
+        ctx.fill()
+
+        start_angle = end_angle
+
+    # Legend
+    ctx.font = "11px system-ui"
+    legend_y = 50
+    for leg_idx in range(len(labels)):
+        leg_label = labels[leg_idx]
+        leg_value = data[leg_label]
+        pct_display = int((leg_value / total) * 100)
+
+        ctx.fillStyle = colors[leg_idx % len(colors)]
+        ctx.fillRect(width - 120, legend_y + leg_idx * 20, 12, 12)
+
+        ctx.fillStyle = "#e2e8f0"
+        ctx.textAlign = "left"
+        ctx.fillText(leg_label + " (" + str(pct_display) + "%)", width - 100, legend_y + leg_idx * 20 + 10)
+
+
+# ============================================================================
+# Dashboard Updates
+# ============================================================================
+
+def update_kpis(data: list):
+    """Update KPI cards."""
+    total_sales = 0
+    total_units = 0
+    for d in data:
+        total_sales += d["sales"]
+        total_units += d["units"]
+
+    avg_order = 0
+    if total_units > 0:
+        avg_order = total_sales / total_units
+
+    sales_values = [d["sales"] for d in data]
+    stats = calculate_stats(sales_values)
+
+    js.document.getElementById("kpi-total-sales").textContent = "$" + str(int(total_sales))
+    js.document.getElementById("kpi-total-units").textContent = str(total_units)
+    js.document.getElementById("kpi-avg-order").textContent = "$" + str(round(avg_order, 2))
+    js.document.getElementById("kpi-best-month").textContent = "$" + str(int(stats['max']))
+
+
+def update_charts(data: list):
+    """Update all charts."""
+    # Sales by region (bar chart)
+    by_region = get_sales_by_region(data)
+    draw_bar_chart("chart-region", by_region, "Sales by Region", "#6366f1")
+
+    # Sales by month (pie chart)
+    by_month = get_sales_by_month(data)
+    draw_pie_chart("chart-month", by_month, "Sales Distribution by Month")
+
+    # Trends by region (line chart)
+    regions = ["North", "South", "East", "West"]
+    trends = {}
+    for r in regions:
+        trends[r] = get_monthly_trend(data, r)
+    draw_line_chart("chart-trend", trends, "Monthly Trend by Region")
+
+
+def update_table(data: list):
+    """Update the data table."""
+    tbody = js.document.getElementById("data-table-body")
+    tbody.innerHTML = ""
+
+    top_entries = get_top_performers(data, 10)
+
+    for entry in top_entries:
+        row = js.document.createElement("tr")
+        html = "<td>" + entry['region'] + "</td>"
+        html += "<td>" + entry['month'] + "</td>"
+        html += "<td>$" + str(entry['sales']) + "</td>"
+        html += "<td>" + str(entry['units']) + "</td>"
+        row.innerHTML = html
+        tbody.appendChild(row)
+
+
+def refresh_dashboard():
+    """Refresh the entire dashboard."""
+    update_kpis(SAMPLE_DATA)
+    update_charts(SAMPLE_DATA)
+    update_table(SAMPLE_DATA)
+
+
+# ============================================================================
+# Filter Handlers
+# ============================================================================
+
+current_filter = "all"
+
+
+def filter_by_region(region: str):
+    """Filter dashboard by region."""
+    global current_filter
+    current_filter = region
+
+    filtered_data = SAMPLE_DATA
+    if region != "all":
+        filtered_data = [d for d in SAMPLE_DATA if d["region"] == region]
+
+    update_kpis(filtered_data)
+    update_charts(filtered_data)
+    update_table(filtered_data)
+
+    # Update active button
+    for btn in js.document.querySelectorAll(".filter-btn"):
+        btn.classList.remove("active")
+    selector = '[data-region="' + region + '"]'
+    js.document.querySelector(selector).classList.add("active")
+
+
+def make_filter_handler(region: str):
+    """Create filter button handler."""
+    def handler(e):
+        filter_by_region(region)
+    return handler
+
+
+# ============================================================================
+# Initialization
+# ============================================================================
+
+def init():
+    """Initialize the dashboard."""
+    # Set up filter buttons
+    regions = ["all", "North", "South", "East", "West"]
+    filter_container = js.document.getElementById("filters")
+
+    for region in regions:
+        btn = js.document.createElement("button")
+        btn.textContent = "All Regions" if region == "all" else region
+        btn.className = "filter-btn"
+        if region == "all":
+            btn.className += " active"
+        btn.dataset.region = region
+        btn.addEventListener("click", make_filter_handler(region))
+        filter_container.appendChild(btn)
+
+    # Initial render
+    refresh_dashboard()
+
+
+# Initialize on load
+js.window.addEventListener("DOMContentLoaded", lambda e: init())
diff --git a/demos/edge-worker/Makefile b/demos/edge-worker/Makefile
new file mode 100644
index 0000000..fea025c
--- /dev/null
+++ b/demos/edge-worker/Makefile
@@ -0,0 +1,18 @@
+.PHONY: build dev deploy clean
+
+build:
+	py2js src/worker.py -o dist/worker.js
+
+dev: build
+	@echo "To test with Wrangler:"
+	@echo "  npx wrangler dev dist/worker.js"
+	@echo ""
+	@echo "Or test locally with Node.js miniflare:"
+	@echo "  npx miniflare dist/worker.js"
+
+deploy: build
+	@echo "To deploy to Cloudflare Workers:"
+	@echo "  npx wrangler deploy"
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/edge-worker/README.md b/demos/edge-worker/README.md
new file mode 100644
index 0000000..e580b7b
--- /dev/null
+++ b/demos/edge-worker/README.md
@@ -0,0 +1,92 @@
+# Edge Worker Demo - Cloudflare Workers in Python
+
+Write edge computing logic in Python, deploy to Cloudflare's global network.
+
+## Use Case
+
+Edge workers run JavaScript on Cloudflare's 300+ data centers worldwide.
+With Prescrypt, you can write that logic in Python:
+
+- **Request filtering**: Bot detection, geo-blocking
+- **A/B testing**: Consistent variant assignment
+- **Response transformation**: Inject headers, modify HTML
+- **Rate limiting**: Protect your origin
+- **Caching strategies**: Custom cache keys, stale-while-revalidate
+
+## Features Demonstrated
+
+```python
+# Bot detection
+def is_bot(user_agent: str) -> bool:
+    ua_lower = user_agent.lower()
+    for pattern in ["bot", "crawler", "spider"]:
+        if pattern in ua_lower:
+            return True
+    return False
+
+# A/B test assignment
+def get_ab_variant(client_ip: str) -> str:
+    h = hash_string(client_ip)
+    # Deterministic assignment based on IP hash
+    ...
+
+# Security headers
+def add_security_headers(response):
+    headers.set("X-Content-Type-Options", "nosniff")
+    headers.set("X-Frame-Options", "DENY")
+    ...
+```
+
+## Build
+
+```bash
+make build   # Compile Python to JavaScript
+```
+
+## Test Locally
+
+Using [Miniflare](https://miniflare.dev/) (Cloudflare Workers simulator):
+
+```bash
+npm install -g miniflare
+make build
+miniflare dist/worker.js
+```
+
+Or with Wrangler:
+
+```bash
+npm install -g wrangler
+wrangler dev dist/worker.js
+```
+
+## Deploy to Cloudflare
+
+1. Sign up at [Cloudflare Workers](https://workers.cloudflare.com/)
+2. Configure `wrangler.toml` with your account
+3. Run:
+
+```bash
+wrangler login
+wrangler deploy
+```
+
+## Why Prescrypt for Edge?
+
+| Metric | Prescrypt | Pyodide |
+|--------|-----------|---------|
+| Bundle size | ~20 KB | 10+ MB |
+| Cold start | <5 ms | N/A (too large) |
+| Memory | ~10 MB | 128+ MB |
+
+Cloudflare Workers have strict limits (1 MB bundle, 128 MB memory).
+Prescrypt fits easily; Pyodide does not.
+
+## Production Enhancements
+
+For production use, consider:
+
+- **KV Storage**: For rate limit counters, session data
+- **Durable Objects**: For stateful edge logic
+- **Workers Analytics**: Track request patterns
+- **Custom domains**: Route specific paths to your worker
diff --git a/demos/edge-worker/src/worker.py b/demos/edge-worker/src/worker.py
new file mode 100644
index 0000000..d01cc43
--- /dev/null
+++ b/demos/edge-worker/src/worker.py
@@ -0,0 +1,297 @@
+"""Edge Worker - Cloudflare Workers in Python
+
+Write edge computing logic in Python, deploy as JavaScript.
+This worker demonstrates common edge computing patterns:
+
+- Request filtering (bot detection, geo-blocking)
+- Request/response transformation
+- A/B testing
+- Rate limiting
+- Caching strategies
+"""
+
+from __future__ import annotations
+
+import js
+
+# ============================================================================
+# Configuration
+# ============================================================================
+
+# Blocked countries (ISO codes)
+BLOCKED_COUNTRIES = ["XX", "YY"]  # Example placeholder codes
+
+# Bot user agent patterns
+BOT_PATTERNS = [
+    "bot",
+    "crawler",
+    "spider",
+    "scraper",
+    "curl",
+    "wget",
+    "python-requests",
+]
+
+# Rate limit: requests per minute per IP
+RATE_LIMIT = 60
+
+# A/B test configuration
+AB_TEST_VARIANTS = {
+    "control": 0.5,  # 50% get control
+    "variant_a": 0.3,  # 30% get variant A
+    "variant_b": 0.2,  # 20% get variant B
+}
+
+
+# ============================================================================
+# Utilities
+# ============================================================================
+
+
+def is_bot(user_agent: str) -> bool:
+    """Check if the request appears to be from a bot."""
+    if not user_agent:
+        return True  # No user agent is suspicious
+
+    ua_lower = user_agent.lower()
+    for pattern in BOT_PATTERNS:
+        if pattern in ua_lower:
+            return True
+    return False
+
+
+def get_country(request) -> str:
+    """Get country code from Cloudflare headers."""
+    # Cloudflare adds CF-IPCountry header
+    return request.headers.get("CF-IPCountry", "XX")
+
+
+def get_client_ip(request) -> str:
+    """Get client IP from Cloudflare headers."""
+    return request.headers.get("CF-Connecting-IP", "0.0.0.0")
+
+
+def hash_string(s: str) -> int:
+    """Simple hash function for A/B testing."""
+    h = 0
+    for c in s:
+        h = (h * 31 + ord(c)) % (2**32)
+    return h
+
+
+def get_ab_variant(identifier: str) -> str:
+    """Determine A/B test variant for an identifier (e.g., IP or cookie)."""
+    h = hash_string(identifier)
+    value = (h % 1000) / 1000.0  # 0.0 to 1.0
+
+    cumulative = 0.0
+    for variant in AB_TEST_VARIANTS:
+        probability = AB_TEST_VARIANTS[variant]
+        cumulative += probability
+        if value < cumulative:
+            return variant
+    return "control"
+
+
+# ============================================================================
+# Request Handlers
+# ============================================================================
+
+
+def handle_blocked(reason: str):
+    """Return a blocked response."""
+    return js.Response.new(
+        f"Access Denied: {reason}",
+        {"status": 403, "headers": {"Content-Type": "text/plain"}},
+    )
+
+
+def handle_rate_limited():
+    """Return a rate limited response."""
+    return js.Response.new(
+        "Rate limit exceeded. Please try again later.",
+        {"status": 429, "headers": {"Content-Type": "text/plain", "Retry-After": "60"}},
+    )
+
+
+def add_security_headers(response):
+    """Add security headers to response."""
+    headers = js.Headers.new(response.headers)
+
+    # Security headers
+    headers.set("X-Content-Type-Options", "nosniff")
+    headers.set("X-Frame-Options", "DENY")
+    headers.set("X-XSS-Protection", "1; mode=block")
+    headers.set("Referrer-Policy", "strict-origin-when-cross-origin")
+
+    # Custom header to show this was processed by edge
+    headers.set("X-Edge-Processed", "true")
+
+    return js.Response.new(
+        response.body,
+        {
+            "status": response.status,
+            "statusText": response.statusText,
+            "headers": headers,
+        },
+    )
+
+
+def transform_html(html: str, variant: str) -> str:
+    """Transform HTML for A/B testing."""
+    # Inject A/B test variant as data attribute
+    if "<body" in html:
+        html = html.replace("<body", f'<body data-variant="{variant}"')
+
+    # Add variant-specific banner
+    banner = f"""
+    <div style="background: #4f46e5; color: white; padding: 10px; text-align: center;">
+        Edge Worker Demo - Variant: {variant.upper()}
+    </div>
+    """
+    if "<body>" in html:
+        html = html.replace("<body>", f"<body>{banner}")
+
+    return html
+
+
+# ============================================================================
+# Main Handler
+# ============================================================================
+
+
+async def handle_request(request):
+    """
+    Main request handler for the edge worker.
+
+    Flow:
+    1. Bot detection
+    2. Geo-blocking
+    3. Rate limiting
+    4. A/B test assignment
+    5. Fetch from origin
+    6. Response transformation
+    """
+    url = js.URL.new(request.url)
+    user_agent = request.headers.get("User-Agent", "")
+    client_ip = get_client_ip(request)
+    country = get_country(request)
+
+    # --- Step 1: Bot Detection ---
+    if is_bot(user_agent):
+        # For demo, we'll allow but log
+        print(f"[EDGE] Bot detected: {user_agent[:50]}")
+        # In production: return handle_blocked("Bot detected")
+
+    # --- Step 2: Geo-blocking ---
+    if country in BLOCKED_COUNTRIES:
+        return handle_blocked(f"Country {country} is not allowed")
+
+    # --- Step 3: Rate Limiting ---
+    # In production, use Cloudflare KV or Durable Objects for state
+    # For demo, we just log
+    print(f"[EDGE] Request from {client_ip} ({country})")
+
+    # --- Step 4: A/B Test Assignment ---
+    variant = get_ab_variant(client_ip)
+    print(f"[EDGE] A/B variant: {variant}")
+
+    # --- Step 5: Fetch from Origin ---
+    # For this demo, we'll return a synthetic response
+    # In production: response = await js.fetch(request)
+
+    html_content = f"""<!DOCTYPE html>
+<html>
+<head>
+    <title>Edge Worker Demo</title>
+    <style>
+        body {{
+            font-family: system-ui, sans-serif;
+            max-width: 800px;
+            margin: 50px auto;
+            padding: 20px;
+            background: #f8fafc;
+        }}
+        .card {{
+            background: white;
+            border-radius: 12px;
+            padding: 30px;
+            box-shadow: 0 4px 6px rgba(0,0,0,0.1);
+        }}
+        h1 {{ color: #4f46e5; }}
+        .info {{ color: #64748b; margin: 10px 0; }}
+        .badge {{
+            display: inline-block;
+            padding: 4px 12px;
+            border-radius: 20px;
+            font-size: 14px;
+            font-weight: 600;
+        }}
+        .badge.variant {{ background: #ddd6fe; color: #5b21b6; }}
+        .badge.country {{ background: #fef3c7; color: #92400e; }}
+        code {{
+            background: #f1f5f9;
+            padding: 2px 6px;
+            border-radius: 4px;
+        }}
+    </style>
+</head>
+<body>
+    <div class="card">
+        <h1>🌐 Edge Worker Response</h1>
+        <p>This response was generated by a Cloudflare Worker written in Python!</p>
+
+        <div class="info">
+            <strong>Your Info:</strong><br>
+            IP: <code>{client_ip}</code><br>
+            Country: <span class="badge country">{country}</span><br>
+            A/B Variant: <span class="badge variant">{variant}</span>
+        </div>
+
+        <div class="info">
+            <strong>Request Path:</strong> <code>{url.pathname}</code>
+        </div>
+
+        <div class="info">
+            <strong>User Agent:</strong><br>
+            <code style="font-size: 12px;">{user_agent[:100]}...</code>
+        </div>
+
+        <hr style="margin: 20px 0; border: none; border-top: 1px solid #e2e8f0;">
+
+        <p style="color: #64748b; font-size: 14px;">
+            The Python code running this worker was compiled to JavaScript by
+            <a href="https://github.com/abilian/prescrypt" style="color: #4f46e5;">Prescrypt</a>.
+            Edge workers run on Cloudflare's global network with sub-millisecond cold starts.
+        </p>
+    </div>
+</body>
+</html>
+"""
+
+    # --- Step 6: Transform Response ---
+    transformed = transform_html(html_content, variant)
+
+    response = js.Response.new(
+        transformed, {"status": 200, "headers": {"Content-Type": "text/html"}}
+    )
+
+    # Add security headers
+    response = add_security_headers(response)
+
+    return response
+
+
+# ============================================================================
+# Worker Entry Point
+# ============================================================================
+
+
+def handle_fetch(event):
+    """Fetch event handler - Cloudflare Worker entry point."""
+    event.respondWith(handle_request(event.request))
+
+
+# Register the fetch handler
+# In Cloudflare Workers: addEventListener('fetch', handleFetch)
+js.self_.addEventListener("fetch", handle_fetch)
diff --git a/demos/edge-worker/wrangler.toml b/demos/edge-worker/wrangler.toml
new file mode 100644
index 0000000..3c2632a
--- /dev/null
+++ b/demos/edge-worker/wrangler.toml
@@ -0,0 +1,24 @@
+# Cloudflare Workers configuration
+# See: https://developers.cloudflare.com/workers/wrangler/configuration/
+
+name = "python-edge-worker"
+main = "dist/worker.js"
+compatibility_date = "2024-01-01"
+
+# Development settings
+[dev]
+port = 8787
+
+# Environment variables (example)
+[vars]
+ENVIRONMENT = "development"
+
+# KV Namespace bindings (for rate limiting, etc.)
+# [[kv_namespaces]]
+# binding = "RATE_LIMIT_KV"
+# id = "your-kv-namespace-id"
+
+# Routes (production)
+# routes = [
+#   { pattern = "example.com/*", zone_name = "example.com" }
+# ]
diff --git a/demos/python-playground/Makefile b/demos/python-playground/Makefile
new file mode 100644
index 0000000..5afb176
--- /dev/null
+++ b/demos/python-playground/Makefile
@@ -0,0 +1,11 @@
+.PHONY: build serve clean
+
+build:
+	py2js src/playground.py -o dist/playground.js -s
+
+serve: build
+	@echo "Starting Python Playground server at http://localhost:8000"
+	python server.py
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/python-playground/README.md b/demos/python-playground/README.md
new file mode 100644
index 0000000..1a4de95
--- /dev/null
+++ b/demos/python-playground/README.md
@@ -0,0 +1,77 @@
+# Python Playground
+
+An interactive Python learning environment in the browser.
+
+## How It Works
+
+1. User writes Python code in the browser editor
+2. Code is sent to a local compile server
+3. Server uses Prescrypt to compile Python to JavaScript
+4. JavaScript is returned and executed in the browser
+5. Output is captured and displayed
+
+## Quick Start
+
+```bash
+make serve
+```
+
+Then open http://localhost:8000 in your browser.
+
+## Features
+
+- **Live compilation**: Edit Python, click Run, see results instantly
+- **Example library**: Pre-built examples for learning
+- **Keyboard shortcut**: Ctrl+Enter to run
+- **Error handling**: Compilation and runtime errors displayed clearly
+
+## Architecture
+
+```
+Browser                    Server (server.py)
+   │                            │
+   │  POST /compile             │
+   │  { "code": "..." }         │
+   ├───────────────────────────>│
+   │                            │  Prescrypt compile
+   │  { "js": "..." }           │
+   │<───────────────────────────┤
+   │                            │
+   │  eval(js) + capture output │
+   │                            │
+```
+
+## Example Programs
+
+- **Hello World**: Basic print statements
+- **Fibonacci**: Sequence generation with lists
+- **Factorial**: Recursive functions
+- **Prime Sieve**: Sieve of Eratosthenes algorithm
+- **Quicksort**: Recursive sorting with list comprehensions
+- **Classes**: Inheritance with super()
+- **Comprehensions**: List and dict comprehensions
+- **FizzBuzz**: Classic programming exercise
+
+## Use Case
+
+This demonstrates Prescrypt's value for **interactive Python learning platforms**:
+
+- Fast compilation (milliseconds, not seconds)
+- Small output size (<50KB typical)
+- Real Python 3 syntax support
+- Ideal for embedded tutorials and documentation
+
+## Development
+
+```bash
+make build   # Compile frontend
+make serve   # Run server on port 8000
+make clean   # Remove build artifacts
+```
+
+## Files
+
+- `server.py` - Compile server (handles /compile endpoint)
+- `src/playground.py` - Frontend logic (compiled to JS)
+- `index.html` - UI layout and styles
+- `dist/playground.js` - Compiled frontend
diff --git a/demos/python-playground/index.html b/demos/python-playground/index.html
new file mode 100644
index 0000000..7a35d84
--- /dev/null
+++ b/demos/python-playground/index.html
@@ -0,0 +1,311 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Python Playground - Prescrypt Demo</title>
+    <style>
+        :root {
+            --bg: #1e1e2e;
+            --surface: #313244;
+            --text: #cdd6f4;
+            --subtext: #a6adc8;
+            --accent: #89b4fa;
+            --green: #a6e3a1;
+            --red: #f38ba8;
+            --yellow: #f9e2af;
+        }
+
+        * {
+            box-sizing: border-box;
+            margin: 0;
+            padding: 0;
+        }
+
+        body {
+            font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
+            background: var(--bg);
+            color: var(--text);
+            min-height: 100vh;
+            line-height: 1.6;
+        }
+
+        .container {
+            max-width: 1200px;
+            margin: 0 auto;
+            padding: 20px;
+        }
+
+        header {
+            text-align: center;
+            padding: 40px 20px;
+            border-bottom: 1px solid var(--surface);
+        }
+
+        h1 {
+            font-size: 2.5rem;
+            background: linear-gradient(135deg, var(--accent), var(--green));
+            -webkit-background-clip: text;
+            -webkit-text-fill-color: transparent;
+            background-clip: text;
+            margin-bottom: 10px;
+        }
+
+        .subtitle {
+            color: var(--subtext);
+            font-size: 1.1rem;
+        }
+
+        .highlight {
+            color: var(--accent);
+        }
+
+        .main-content {
+            display: grid;
+            grid-template-columns: 250px 1fr;
+            gap: 20px;
+            margin-top: 20px;
+        }
+
+        .sidebar {
+            background: var(--surface);
+            border-radius: 12px;
+            padding: 20px;
+        }
+
+        .sidebar h2 {
+            font-size: 0.9rem;
+            text-transform: uppercase;
+            letter-spacing: 0.1em;
+            color: var(--subtext);
+            margin-bottom: 15px;
+        }
+
+        .example-list {
+            list-style: none;
+        }
+
+        .example-list li {
+            margin-bottom: 8px;
+        }
+
+        .example-btn {
+            width: 100%;
+            padding: 12px 15px;
+            background: transparent;
+            border: 1px solid transparent;
+            border-radius: 8px;
+            color: var(--text);
+            cursor: pointer;
+            text-align: left;
+            font-size: 14px;
+            transition: all 0.2s;
+        }
+
+        .example-btn:hover {
+            background: rgba(137, 180, 250, 0.1);
+            border-color: var(--accent);
+        }
+
+        .example-btn.active {
+            background: rgba(137, 180, 250, 0.2);
+            border-color: var(--accent);
+        }
+
+        .editor-area {
+            display: flex;
+            flex-direction: column;
+            gap: 20px;
+        }
+
+        .panel {
+            background: var(--surface);
+            border-radius: 12px;
+            overflow: hidden;
+        }
+
+        .panel-header {
+            display: flex;
+            justify-content: space-between;
+            align-items: center;
+            padding: 12px 20px;
+            background: rgba(0, 0, 0, 0.2);
+            border-bottom: 1px solid rgba(255, 255, 255, 0.05);
+        }
+
+        .panel-title {
+            font-size: 0.85rem;
+            text-transform: uppercase;
+            letter-spacing: 0.1em;
+            color: var(--subtext);
+        }
+
+        .run-btn {
+            padding: 8px 20px;
+            background: var(--green);
+            color: var(--bg);
+            border: none;
+            border-radius: 6px;
+            font-weight: 600;
+            cursor: pointer;
+            font-size: 14px;
+            transition: all 0.2s;
+        }
+
+        .run-btn:hover {
+            transform: translateY(-1px);
+            box-shadow: 0 4px 12px rgba(166, 227, 161, 0.3);
+        }
+
+        .code-editor {
+            width: 100%;
+            min-height: 300px;
+            padding: 20px;
+            background: transparent;
+            border: none;
+            color: var(--text);
+            font-family: inherit;
+            font-size: 14px;
+            line-height: 1.6;
+            resize: vertical;
+            outline: none;
+        }
+
+        .output {
+            padding: 20px;
+            min-height: 150px;
+            font-size: 14px;
+            white-space: pre-wrap;
+            color: var(--green);
+        }
+
+        .output.error {
+            color: var(--red);
+        }
+
+        .output.empty {
+            color: var(--subtext);
+            font-style: italic;
+        }
+
+        .keyboard-hint {
+            font-size: 12px;
+            color: var(--subtext);
+        }
+
+        kbd {
+            background: var(--bg);
+            padding: 2px 6px;
+            border-radius: 4px;
+            font-size: 11px;
+        }
+
+        .stats {
+            display: flex;
+            gap: 20px;
+            margin-top: 30px;
+            justify-content: center;
+        }
+
+        .stat {
+            text-align: center;
+            padding: 20px 30px;
+            background: var(--surface);
+            border-radius: 12px;
+        }
+
+        .stat-value {
+            font-size: 2rem;
+            font-weight: bold;
+            color: var(--accent);
+        }
+
+        .stat-label {
+            font-size: 0.85rem;
+            color: var(--subtext);
+            margin-top: 5px;
+        }
+
+        @media (max-width: 768px) {
+            .main-content {
+                grid-template-columns: 1fr;
+            }
+
+            .sidebar {
+                order: -1;
+            }
+
+            .example-list {
+                display: flex;
+                flex-wrap: wrap;
+                gap: 8px;
+            }
+
+            .example-list li {
+                margin: 0;
+            }
+
+            .example-btn {
+                width: auto;
+            }
+        }
+    </style>
+</head>
+<body>
+    <header>
+        <h1>Python Playground</h1>
+        <p class="subtitle">
+            Write Python, compile to JavaScript, run in your browser.
+            <span class="highlight">Powered by Prescrypt.</span>
+        </p>
+    </header>
+
+    <div class="container">
+        <div class="main-content">
+            <aside class="sidebar">
+                <h2>Examples</h2>
+                <ul class="example-list" id="examples"></ul>
+            </aside>
+
+            <main class="editor-area">
+                <div class="panel">
+                    <div class="panel-header">
+                        <span class="panel-title">Python Code</span>
+                        <div>
+                            <span class="keyboard-hint"><kbd>Ctrl</kbd>+<kbd>Enter</kbd> to run</span>
+                            <button class="run-btn" id="run-btn">Run</button>
+                        </div>
+                    </div>
+                    <textarea id="code-editor" class="code-editor" spellcheck="false"># Hello World
+print("Hello, World!")
+print("Welcome to Python!")</textarea>
+                </div>
+
+                <div class="panel">
+                    <div class="panel-header">
+                        <span class="panel-title">Output</span>
+                    </div>
+                    <div id="output" class="output empty">(Click "Run" to execute)</div>
+                </div>
+            </main>
+        </div>
+
+        <div class="stats">
+            <div class="stat">
+                <div class="stat-value">&lt;50KB</div>
+                <div class="stat-label">Output Size</div>
+            </div>
+            <div class="stat">
+                <div class="stat-value">Fast</div>
+                <div class="stat-label">Compilation</div>
+            </div>
+            <div class="stat">
+                <div class="stat-value">Python 3</div>
+                <div class="stat-label">Syntax Support</div>
+            </div>
+        </div>
+    </div>
+
+    <script type="module" src="dist/playground.js"></script>
+</body>
+</html>
diff --git a/demos/python-playground/server.py b/demos/python-playground/server.py
new file mode 100644
index 0000000..c271a6e
--- /dev/null
+++ b/demos/python-playground/server.py
@@ -0,0 +1,84 @@
+"""Simple compile server for the Python Playground.
+
+Receives Python code via POST and returns compiled JavaScript.
+"""
+import json
+from http.server import HTTPServer, SimpleHTTPRequestHandler
+from urllib.parse import urlparse
+
+from prescrypt.compiler import Compiler
+
+
+class PlaygroundHandler(SimpleHTTPRequestHandler):
+    """Handler that serves static files and handles /compile endpoint."""
+
+    def do_POST(self):
+        """Handle POST requests to /compile."""
+        path = urlparse(self.path).path
+
+        if path == "/compile":
+            self.handle_compile()
+        else:
+            self.send_error(404, "Not Found")
+
+    def handle_compile(self):
+        """Compile Python code to JavaScript."""
+        # Read request body
+        content_length = int(self.headers.get("Content-Length", 0))
+        body = self.rfile.read(content_length).decode("utf-8")
+
+        try:
+            data = json.loads(body)
+            python_code = data.get("code", "")
+
+            # Compile to JavaScript
+            compiler = Compiler()
+            js_code = compiler.compile(
+                python_code,
+                include_stdlib=True,
+                tree_shake=True,
+            )
+
+            # Send success response
+            self.send_response(200)
+            self.send_header("Content-Type", "application/json")
+            self.send_header("Access-Control-Allow-Origin", "*")
+            self.end_headers()
+
+            response = json.dumps({"success": True, "js": js_code})
+            self.wfile.write(response.encode("utf-8"))
+
+        except Exception as e:
+            # Send error response
+            self.send_response(200)  # Use 200 so JS can read the error
+            self.send_header("Content-Type", "application/json")
+            self.send_header("Access-Control-Allow-Origin", "*")
+            self.end_headers()
+
+            response = json.dumps({"success": False, "error": str(e)})
+            self.wfile.write(response.encode("utf-8"))
+
+    def do_OPTIONS(self):
+        """Handle CORS preflight."""
+        self.send_response(200)
+        self.send_header("Access-Control-Allow-Origin", "*")
+        self.send_header("Access-Control-Allow-Methods", "POST, OPTIONS")
+        self.send_header("Access-Control-Allow-Headers", "Content-Type")
+        self.end_headers()
+
+    def end_headers(self):
+        """Add CORS headers to all responses."""
+        self.send_header("Access-Control-Allow-Origin", "*")
+        super().end_headers()
+
+
+def main():
+    port = 8000
+    server = HTTPServer(("", port), PlaygroundHandler)
+    print(f"Python Playground server running at http://localhost:{port}")
+    print("Press Ctrl+C to stop")
+    server.serve_forever()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/demos/python-playground/src/playground.py b/demos/python-playground/src/playground.py
new file mode 100644
index 0000000..61ed2ab
--- /dev/null
+++ b/demos/python-playground/src/playground.py
@@ -0,0 +1,405 @@
+"""Interactive Python Playground
+
+A browser-based Python learning environment with server-side compilation.
+Write Python code, compile it to JavaScript via the server, and run it instantly.
+"""
+import js
+
+
+# ============================================================================
+# Example Programs
+# ============================================================================
+
+EXAMPLES = [
+    {
+        "name": "hello",
+        "title": "Hello World",
+        "code": '''# Hello World - Your First Program
+print("Hello, World!")
+print("Welcome to Python in the browser!")
+print()
+print("This code is compiled to JavaScript")
+print("by Prescrypt and runs in your browser.")
+''',
+    },
+    {
+        "name": "fibonacci",
+        "title": "Fibonacci",
+        "code": '''# Fibonacci Sequence
+def fibonacci(n):
+    """Generate first n Fibonacci numbers."""
+    fib = [0, 1]
+    for i in range(2, n):
+        fib.append(fib[i-1] + fib[i-2])
+    return fib[:n]
+
+result = fibonacci(15)
+print("Fibonacci sequence (first 15 numbers):")
+print(result)
+print()
+print("Sum:", sum(result))
+''',
+    },
+    {
+        "name": "factorial",
+        "title": "Factorial",
+        "code": '''# Factorial with Recursion
+def factorial(n):
+    """Calculate n! recursively."""
+    if n <= 1:
+        return 1
+    return n * factorial(n - 1)
+
+print("Factorials from 0 to 10:")
+for i in range(11):
+    print(str(i) + "! = " + str(factorial(i)))
+''',
+    },
+    {
+        "name": "primes",
+        "title": "Prime Sieve",
+        "code": '''# Sieve of Eratosthenes
+def sieve(limit):
+    """Find all primes up to limit."""
+    is_prime = [True] * (limit + 1)
+    is_prime[0] = False
+    is_prime[1] = False
+
+    i = 2
+    while i * i <= limit:
+        if is_prime[i]:
+            j = i * i
+            while j <= limit:
+                is_prime[j] = False
+                j += i
+        i += 1
+
+    result = []
+    for i in range(limit + 1):
+        if is_prime[i]:
+            result.append(i)
+    return result
+
+primes = sieve(50)
+print("Prime numbers up to 50:")
+print(primes)
+print()
+print("Count:", len(primes))
+''',
+    },
+    {
+        "name": "sorting",
+        "title": "Quicksort",
+        "code": '''# Quicksort Algorithm
+def quicksort(arr):
+    """Classic quicksort implementation."""
+    if len(arr) <= 1:
+        return arr
+    pivot = arr[len(arr) // 2]
+    left = [x for x in arr if x < pivot]
+    middle = [x for x in arr if x == pivot]
+    right = [x for x in arr if x > pivot]
+    return quicksort(left) + middle + quicksort(right)
+
+numbers = [64, 34, 25, 12, 22, 11, 90, 42, 88, 7]
+print("Original:", numbers)
+print("Sorted:  ", quicksort(numbers))
+''',
+    },
+    {
+        "name": "classes",
+        "title": "Classes",
+        "code": '''# Classes and Inheritance
+class Animal:
+    def __init__(self, name, sound):
+        self.name = name
+        self.sound = sound
+
+    def speak(self):
+        return self.name + " says " + self.sound + "!"
+
+class Dog(Animal):
+    def __init__(self, name):
+        super().__init__(name, "Woof")
+
+    def fetch(self):
+        return self.name + " fetches the ball!"
+
+class Cat(Animal):
+    def __init__(self, name):
+        super().__init__(name, "Meow")
+
+rex = Dog("Rex")
+print(rex.speak())
+print(rex.fetch())
+print()
+
+whiskers = Cat("Whiskers")
+print(whiskers.speak())
+''',
+    },
+    {
+        "name": "comprehensions",
+        "title": "Comprehensions",
+        "code": '''# Python Comprehensions
+
+# List comprehension
+squares = [x * x for x in range(1, 11)]
+print("Squares 1-10:", squares)
+
+# Filtered comprehension
+evens = [x for x in range(20) if x % 2 == 0]
+print("Even numbers:", evens)
+
+# Dict comprehension
+word = "hello"
+counts = {}
+for c in word:
+    counts[c] = word.count(c)
+print("Letter counts in 'hello':", counts)
+''',
+    },
+    {
+        "name": "fizzbuzz",
+        "title": "FizzBuzz",
+        "code": '''# FizzBuzz - Classic Interview Problem
+result = []
+for i in range(1, 31):
+    if i % 15 == 0:
+        result.append("FizzBuzz")
+    elif i % 3 == 0:
+        result.append("Fizz")
+    elif i % 5 == 0:
+        result.append("Buzz")
+    else:
+        result.append(str(i))
+
+print("FizzBuzz 1-30:")
+print(result)
+''',
+    },
+]
+
+
+# ============================================================================
+# State
+# ============================================================================
+
+current_example = None
+is_compiling = False
+
+
+# ============================================================================
+# UI Functions
+# ============================================================================
+
+def select_example(example):
+    """Select and display an example."""
+    global current_example
+    current_example = example
+
+    # Update editor
+    editor = js.document.getElementById("code-editor")
+    editor.value = example["code"]
+
+    # Update active button
+    for b in js.document.querySelectorAll(".example-btn"):
+        b.classList.remove("active")
+
+    active_btn = js.document.querySelector('[data-example="' + example["name"] + '"]')
+    if active_btn:
+        active_btn.classList.add("active")
+
+    # Clear output
+    output_el = js.document.getElementById("output")
+    output_el.textContent = '(Click "Run" to execute)'
+    output_el.className = "output empty"
+
+
+def show_output(text, is_error=False):
+    """Display output in the output panel."""
+    output_el = js.document.getElementById("output")
+    if text:
+        output_el.textContent = text
+        output_el.className = "output error" if is_error else "output"
+    else:
+        output_el.textContent = "(No output)"
+        output_el.className = "output empty"
+
+
+def show_compiling():
+    """Show compiling state."""
+    output_el = js.document.getElementById("output")
+    output_el.textContent = "Compiling..."
+    output_el.className = "output empty"
+
+    run_btn = js.document.getElementById("run-btn")
+    run_btn.textContent = "Compiling..."
+    run_btn.disabled = True
+
+
+def hide_compiling():
+    """Hide compiling state."""
+    run_btn = js.document.getElementById("run-btn")
+    run_btn.textContent = "Run"
+    run_btn.disabled = False
+
+
+# ============================================================================
+# Compilation and Execution
+# ============================================================================
+
+def execute_js(js_code):
+    """Execute compiled JavaScript and capture output."""
+    # Intercept console.log since Prescrypt's print() uses it internally
+    wrapper_code = """
+    (function() {
+        var _output = [];
+        var _originalLog = console.log;
+
+        // Override console.log to capture output
+        console.log = function() {
+            var args = Array.prototype.slice.call(arguments);
+            var text = args.map(function(a) {
+                if (a === null) return 'None';
+                if (a === undefined) return 'None';
+                if (Array.isArray(a)) return '[' + a.join(', ') + ']';
+                if (typeof a === 'object') return JSON.stringify(a);
+                return String(a);
+            }).join(' ');
+            _output.push(text);
+        };
+
+        try {
+            """ + js_code + """
+        } catch (e) {
+            console.log = _originalLog;
+            return {error: e.toString()};
+        }
+
+        console.log = _originalLog;
+        return {output: _output.join('\\n')};
+    })()
+    """
+
+    try:
+        result = js.eval(wrapper_code)
+        if result.error:
+            return {"error": result.error}
+        return {"output": result.output}
+    except Exception as e:
+        return {"error": str(e)}
+
+
+def handle_compile_response(response):
+    """Handle the response from the compile server."""
+    global is_compiling
+    is_compiling = False
+    hide_compiling()
+
+    try:
+        data = js.JSON.parse(response)
+
+        if not data.success:
+            show_output("Compilation error: " + str(data.error), is_error=True)
+            return
+
+        # Execute the compiled JavaScript
+        result = execute_js(data.js)
+
+        if "error" in result and result["error"]:
+            show_output("Runtime error: " + result["error"], is_error=True)
+        else:
+            show_output(result.get("output", ""))
+
+    except Exception as e:
+        show_output("Error: " + str(e), is_error=True)
+
+
+def handle_compile_error(error):
+    """Handle compilation error."""
+    global is_compiling
+    is_compiling = False
+    hide_compiling()
+    show_output("Failed to connect to compile server. Make sure it's running:\n\n  python server.py", is_error=True)
+
+
+def run_code():
+    """Compile and run the code in the editor."""
+    global is_compiling
+
+    if is_compiling:
+        return
+
+    is_compiling = True
+    show_compiling()
+
+    editor = js.document.getElementById("code-editor")
+    code = editor.value
+
+    # Send to compile server
+    # Create options object, then assign body separately to keep it as a string
+    fetch_options = js.eval("({method: 'POST', headers: {'Content-Type': 'application/json'}})")
+    fetch_options.body = js.JSON.stringify({"code": code})
+
+    def on_response(response):
+        response.text().then(handle_compile_response).catch(handle_compile_error)
+
+    js.fetch("/compile", fetch_options).then(on_response).catch(handle_compile_error)
+
+
+# ============================================================================
+# Event Handlers
+# ============================================================================
+
+def make_example_handler(example):
+    """Create click handler for example button."""
+    def handler(e):
+        select_example(example)
+    return handler
+
+
+def handle_keydown(e):
+    """Handle keyboard shortcuts."""
+    if (e.ctrlKey or e.metaKey) and e.key == "Enter":
+        e.preventDefault()
+        run_code()
+
+
+def handle_run_click(e):
+    """Handle run button click."""
+    run_code()
+
+
+# ============================================================================
+# Initialization
+# ============================================================================
+
+def init():
+    """Initialize the playground."""
+    # Create example buttons
+    examples_list = js.document.getElementById("examples")
+    for example in EXAMPLES:
+        li = js.document.createElement("li")
+        btn = js.document.createElement("button")
+        btn.textContent = example["title"]
+        btn.className = "example-btn"
+        btn.dataset.example = example["name"]
+        btn.addEventListener("click", make_example_handler(example))
+        li.appendChild(btn)
+        examples_list.appendChild(li)
+
+    # Run button
+    run_btn = js.document.getElementById("run-btn")
+    run_btn.addEventListener("click", handle_run_click)
+
+    # Keyboard shortcuts
+    editor = js.document.getElementById("code-editor")
+    editor.addEventListener("keydown", handle_keydown)
+
+    # Load first example
+    select_example(EXAMPLES[0])
+
+
+# Initialize on load
+js.window.addEventListener("DOMContentLoaded", lambda e: init())
diff --git a/demos/simulation/Makefile b/demos/simulation/Makefile
new file mode 100644
index 0000000..da8f84a
--- /dev/null
+++ b/demos/simulation/Makefile
@@ -0,0 +1,10 @@
+.PHONY: build serve clean
+
+build:
+	py2js src/simulation.py -o dist/simulation.js -s
+
+serve: build
+	python -m http.server 8002
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/simulation/README.md b/demos/simulation/README.md
new file mode 100644
index 0000000..c163d4e
--- /dev/null
+++ b/demos/simulation/README.md
@@ -0,0 +1,60 @@
+# Predator-Prey Ecosystem Simulation
+
+An interactive Lotka-Volterra simulation demonstrating scientific computing in the browser.
+
+## Use Case
+
+Perfect for **educational widgets** embedded in:
+- Online textbooks
+- Course materials (Canvas, Moodle)
+- Blog posts and articles
+- Scientific documentation
+
+## Features
+
+- **Real-time visualization** of population dynamics
+- **Phase space plot** showing the limit cycle
+- **Interactive parameters** - adjust birth rates, predation, etc.
+- **Pure Python** simulation logic compiled to JavaScript
+
+## The Model
+
+The [Lotka-Volterra equations](https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations) model predator-prey dynamics:
+
+```
+dPrey/dt = αP - βPF       (prey growth minus predation)
+dPredators/dt = δPF - γF  (predator growth minus death)
+```
+
+## Build & Run
+
+```bash
+make build   # Compile Python to JavaScript
+make serve   # Start server on port 8002
+```
+
+Then open http://localhost:8002
+
+## Technical Highlights
+
+- Numerical integration (Euler method)
+- Canvas 2D rendering
+- Animation frame loop
+- Parameter class with defaults
+- Real-time chart updates
+
+## Why Prescrypt?
+
+Compare to alternatives:
+- **Pyodide**: 10+ MB download, 5-10 second load time
+- **Prescrypt**: ~30 KB download, instant load
+
+For educational widgets that need to load fast and work offline, Prescrypt is ideal.
+
+## Customization Ideas
+
+- Add noise/stochasticity
+- Multiple prey species
+- Seasonal variation in birth rates
+- Carrying capacity limits
+- Geographic spread (2D grid)
diff --git a/demos/simulation/index.html b/demos/simulation/index.html
new file mode 100644
index 0000000..4773963
--- /dev/null
+++ b/demos/simulation/index.html
@@ -0,0 +1,348 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Predator-Prey Simulation - Prescrypt Demo</title>
+    <style>
+        :root {
+            --bg: #0f172a;
+            --surface: #1e293b;
+            --border: #334155;
+            --text: #e2e8f0;
+            --text-muted: #94a3b8;
+            --accent: #8b5cf6;
+            --prey: #3b82f6;
+            --predator: #ef4444;
+        }
+
+        * {
+            box-sizing: border-box;
+            margin: 0;
+            padding: 0;
+        }
+
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+            background: var(--bg);
+            color: var(--text);
+            min-height: 100vh;
+            line-height: 1.6;
+        }
+
+        .container {
+            max-width: 1100px;
+            margin: 0 auto;
+            padding: 30px 20px;
+        }
+
+        header {
+            text-align: center;
+            margin-bottom: 30px;
+        }
+
+        h1 {
+            font-size: 2rem;
+            background: linear-gradient(135deg, var(--prey), var(--predator));
+            -webkit-background-clip: text;
+            -webkit-text-fill-color: transparent;
+            background-clip: text;
+            margin-bottom: 10px;
+        }
+
+        .subtitle {
+            color: var(--text-muted);
+        }
+
+        .main-layout {
+            display: grid;
+            grid-template-columns: 1fr 300px;
+            gap: 20px;
+        }
+
+        .charts {
+            display: flex;
+            flex-direction: column;
+            gap: 20px;
+        }
+
+        .chart-container {
+            background: var(--surface);
+            border-radius: 12px;
+            padding: 20px;
+        }
+
+        .chart-title {
+            font-size: 0.9rem;
+            color: var(--text-muted);
+            text-transform: uppercase;
+            letter-spacing: 0.05em;
+            margin-bottom: 15px;
+        }
+
+        canvas {
+            display: block;
+            border-radius: 8px;
+            width: 100%;
+            height: auto;
+        }
+
+        .sidebar {
+            background: var(--surface);
+            border-radius: 12px;
+            padding: 20px;
+        }
+
+        .sidebar h2 {
+            font-size: 1rem;
+            margin-bottom: 20px;
+            color: var(--accent);
+        }
+
+        .param-group {
+            margin-bottom: 20px;
+        }
+
+        .param-group h3 {
+            font-size: 0.8rem;
+            color: var(--text-muted);
+            text-transform: uppercase;
+            letter-spacing: 0.05em;
+            margin-bottom: 12px;
+            padding-bottom: 8px;
+            border-bottom: 1px solid var(--border);
+        }
+
+        .param {
+            margin-bottom: 12px;
+        }
+
+        .param label {
+            display: flex;
+            justify-content: space-between;
+            font-size: 13px;
+            margin-bottom: 4px;
+        }
+
+        .param-value {
+            color: var(--accent);
+            font-weight: 500;
+        }
+
+        input[type="range"] {
+            width: 100%;
+            height: 6px;
+            -webkit-appearance: none;
+            background: var(--border);
+            border-radius: 3px;
+            outline: none;
+        }
+
+        input[type="range"]::-webkit-slider-thumb {
+            -webkit-appearance: none;
+            width: 16px;
+            height: 16px;
+            background: var(--accent);
+            border-radius: 50%;
+            cursor: pointer;
+        }
+
+        .controls {
+            display: flex;
+            gap: 10px;
+            margin-top: 20px;
+        }
+
+        button {
+            flex: 1;
+            padding: 12px;
+            border: none;
+            border-radius: 8px;
+            font-size: 14px;
+            font-weight: 600;
+            cursor: pointer;
+            transition: all 0.2s;
+        }
+
+        button:disabled {
+            opacity: 0.5;
+            cursor: not-allowed;
+        }
+
+        #start-btn {
+            background: var(--accent);
+            color: white;
+        }
+
+        #start-btn:hover:not(:disabled) {
+            filter: brightness(1.1);
+        }
+
+        #stop-btn {
+            background: var(--predator);
+            color: white;
+        }
+
+        #reset-btn {
+            background: var(--border);
+            color: var(--text);
+        }
+
+        .equation-box {
+            background: var(--bg);
+            border-radius: 8px;
+            padding: 15px;
+            margin-top: 20px;
+            font-family: 'Times New Roman', serif;
+            font-size: 14px;
+        }
+
+        .equation-box h4 {
+            font-family: -apple-system, sans-serif;
+            font-size: 0.75rem;
+            color: var(--text-muted);
+            text-transform: uppercase;
+            margin-bottom: 10px;
+        }
+
+        .equation {
+            color: var(--text);
+            margin: 8px 0;
+        }
+
+        .prey-color {
+            color: var(--prey);
+        }
+
+        .predator-color {
+            color: var(--predator);
+        }
+
+        .info-text {
+            font-size: 12px;
+            color: var(--text-muted);
+            margin-top: 20px;
+            padding-top: 15px;
+            border-top: 1px solid var(--border);
+        }
+
+        @media (max-width: 900px) {
+            .main-layout {
+                grid-template-columns: 1fr;
+            }
+
+            .sidebar {
+                order: -1;
+            }
+        }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <header>
+            <h1>🦊 Predator-Prey Ecosystem 🐰</h1>
+            <p class="subtitle">Interactive Lotka-Volterra simulation - Python running in your browser</p>
+        </header>
+
+        <div class="main-layout">
+            <div class="charts">
+                <div class="chart-container">
+                    <div class="chart-title">Population Over Time</div>
+                    <canvas id="sim-canvas"></canvas>
+                </div>
+                <div class="chart-container">
+                    <div class="chart-title">Phase Space (Limit Cycle)</div>
+                    <canvas id="phase-canvas"></canvas>
+                </div>
+            </div>
+
+            <aside class="sidebar">
+                <h2>Parameters</h2>
+
+                <div class="param-group">
+                    <h3>Initial Populations</h3>
+                    <div class="param">
+                        <label>
+                            <span class="prey-color">Prey (Rabbits)</span>
+                            <span class="param-value" id="initial-prey-val">100</span>
+                        </label>
+                        <input type="range" id="initial-prey" min="10" max="200" value="100"
+                               oninput="document.getElementById('initial-prey-val').textContent=this.value">
+                    </div>
+                    <div class="param">
+                        <label>
+                            <span class="predator-color">Predators (Foxes)</span>
+                            <span class="param-value" id="initial-predators-val">20</span>
+                        </label>
+                        <input type="range" id="initial-predators" min="5" max="100" value="20"
+                               oninput="document.getElementById('initial-predators-val').textContent=this.value">
+                    </div>
+                </div>
+
+                <div class="param-group">
+                    <h3>Prey Parameters</h3>
+                    <div class="param">
+                        <label>
+                            Birth Rate (α)
+                            <span class="param-value" id="birth-rate-val">0.10</span>
+                        </label>
+                        <input type="range" id="birth-rate" min="0.01" max="0.3" step="0.01" value="0.1"
+                               oninput="document.getElementById('birth-rate-val').textContent=parseFloat(this.value).toFixed(2)">
+                    </div>
+                    <div class="param">
+                        <label>
+                            Predation Rate (β)
+                            <span class="param-value" id="predation-rate-val">0.02</span>
+                        </label>
+                        <input type="range" id="predation-rate" min="0.005" max="0.05" step="0.005" value="0.02"
+                               oninput="document.getElementById('predation-rate-val').textContent=parseFloat(this.value).toFixed(3)">
+                    </div>
+                </div>
+
+                <div class="param-group">
+                    <h3>Predator Parameters</h3>
+                    <div class="param">
+                        <label>
+                            Death Rate (γ)
+                            <span class="param-value" id="death-rate-val">0.10</span>
+                        </label>
+                        <input type="range" id="death-rate" min="0.01" max="0.3" step="0.01" value="0.1"
+                               oninput="document.getElementById('death-rate-val').textContent=parseFloat(this.value).toFixed(2)">
+                    </div>
+                    <div class="param">
+                        <label>
+                            Conversion Rate (δ)
+                            <span class="param-value" id="conversion-rate-val">0.01</span>
+                        </label>
+                        <input type="range" id="conversion-rate" min="0.005" max="0.03" step="0.001" value="0.01"
+                               oninput="document.getElementById('conversion-rate-val').textContent=parseFloat(this.value).toFixed(3)">
+                    </div>
+                </div>
+
+                <div class="controls">
+                    <button id="start-btn">▶ Start</button>
+                    <button id="stop-btn" disabled>⏸ Pause</button>
+                    <button id="reset-btn">↺ Reset</button>
+                </div>
+
+                <div class="equation-box">
+                    <h4>Lotka-Volterra Equations</h4>
+                    <div class="equation">
+                        d<span class="prey-color">P</span>/dt = α<span class="prey-color">P</span> − β<span class="prey-color">P</span><span class="predator-color">F</span>
+                    </div>
+                    <div class="equation">
+                        d<span class="predator-color">F</span>/dt = δ<span class="prey-color">P</span><span class="predator-color">F</span> − γ<span class="predator-color">F</span>
+                    </div>
+                </div>
+
+                <p class="info-text">
+                    This simulation runs entirely in your browser. The Python code
+                    was compiled to JavaScript by Prescrypt - no server needed!
+                </p>
+            </aside>
+        </div>
+    </div>
+
+    <script type="module" src="dist/simulation.js"></script>
+</body>
+</html>
diff --git a/demos/simulation/src/simulation.py b/demos/simulation/src/simulation.py
new file mode 100644
index 0000000..ca6934a
--- /dev/null
+++ b/demos/simulation/src/simulation.py
@@ -0,0 +1,438 @@
+"""Predator-Prey Ecosystem Simulation
+
+An interactive Lotka-Volterra simulation demonstrating scientific computing
+in the browser. Perfect for educational widgets embedded in textbooks,
+course materials, or blog posts.
+
+The model simulates:
+- Rabbits (prey): grow exponentially, eaten by foxes
+- Foxes (predators): grow based on prey availability, die without food
+"""
+from __future__ import annotations
+
+import js
+
+# ============================================================================
+# Simulation Parameters
+# ============================================================================
+
+class SimulationParams:
+    """Parameters for the Lotka-Volterra model."""
+
+    def __init__(self):
+        # Prey (rabbit) parameters
+        self.prey_birth_rate = 0.1      # Natural growth rate
+        self.predation_rate = 0.02      # Rate at which predators eat prey
+
+        # Predator (fox) parameters
+        self.predator_death_rate = 0.1  # Natural death rate
+        self.conversion_rate = 0.01     # Efficiency of converting prey to predators
+
+        # Initial populations
+        self.initial_prey = 100
+        self.initial_predators = 20
+
+        # Simulation settings
+        self.dt = 0.1                   # Time step
+        self.max_time = 200             # Total simulation time
+
+
+# ============================================================================
+# Lotka-Volterra Model
+# ============================================================================
+
+def lotka_volterra_step(prey: float, predators: float, params: SimulationParams) -> tuple:
+    """
+    Perform one step of the Lotka-Volterra equations.
+
+    dPrey/dt = α*Prey - β*Prey*Predators
+    dPredators/dt = δ*Prey*Predators - γ*Predators
+
+    Where:
+    - α = prey birth rate
+    - β = predation rate
+    - γ = predator death rate
+    - δ = conversion rate
+    """
+    # Change in prey population
+    prey_change = (
+        params.prey_birth_rate * prey
+        - params.predation_rate * prey * predators
+    ) * params.dt
+
+    # Change in predator population
+    predator_change = (
+        params.conversion_rate * prey * predators
+        - params.predator_death_rate * predators
+    ) * params.dt
+
+    # Update populations (ensure non-negative)
+    new_prey = max(0, prey + prey_change)
+    new_predators = max(0, predators + predator_change)
+
+    return new_prey, new_predators
+
+
+def run_simulation(params: SimulationParams) -> dict:
+    """
+    Run the full simulation and return time series data.
+    """
+    steps = int(params.max_time / params.dt)
+
+    times = []
+    prey_history = []
+    predator_history = []
+
+    prey = params.initial_prey
+    predators = params.initial_predators
+    time = 0.0
+
+    for _ in range(steps):
+        times.append(time)
+        prey_history.append(prey)
+        predator_history.append(predators)
+
+        result = lotka_volterra_step(prey, predators, params)
+        prey = result[0]
+        predators = result[1]
+        time += params.dt
+
+        # Stop if both populations die out
+        if prey < 0.01 and predators < 0.01:
+            break
+
+    return {
+        "times": times,
+        "prey": prey_history,
+        "predators": predator_history,
+    }
+
+
+# ============================================================================
+# Visualization
+# ============================================================================
+
+canvas = None
+ctx = None
+animation_frame = None
+is_running = False
+
+# Current simulation state
+current_step = 0
+sim_data = None
+params = None
+
+
+def draw_axes():
+    """Draw chart axes."""
+    width = canvas.width
+    height = canvas.height
+    padding = 50
+
+    ctx.strokeStyle = "#64748b"
+    ctx.lineWidth = 1
+
+    # Y axis
+    ctx.beginPath()
+    ctx.moveTo(padding, padding)
+    ctx.lineTo(padding, height - padding)
+    ctx.stroke()
+
+    # X axis
+    ctx.beginPath()
+    ctx.moveTo(padding, height - padding)
+    ctx.lineTo(width - padding, height - padding)
+    ctx.stroke()
+
+    # Labels
+    ctx.fillStyle = "#64748b"
+    ctx.font = "12px system-ui"
+    ctx.fillText("Time", width // 2, height - 10)
+
+    ctx.save()
+    ctx.translate(15, height // 2)
+    ctx.rotate(-3.14159 / 2)
+    ctx.fillText("Population", 0, 0)
+    ctx.restore()
+
+
+def draw_chart(data: dict, max_step: int):
+    """Draw the population chart up to max_step."""
+    width = canvas.width
+    height = canvas.height
+    padding = 50
+
+    # Clear canvas
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, width, height)
+
+    draw_axes()
+
+    if max_step < 2:
+        return
+
+    # Calculate scale
+    times = data["times"][:max_step]
+    prey = data["prey"][:max_step]
+    predators = data["predators"][:max_step]
+
+    max_time = times[-1] if times else 1
+    max_pop = max(max(prey), max(predators), 1)
+
+    chart_width = width - 2 * padding
+    chart_height = height - 2 * padding
+
+    def x_scale(t):
+        return padding + (t / max_time) * chart_width
+
+    def y_scale(p):
+        return height - padding - (p / max_pop) * chart_height
+
+    # Draw prey line (blue)
+    ctx.strokeStyle = "#3b82f6"
+    ctx.lineWidth = 2
+    ctx.beginPath()
+    for i, (t, p) in enumerate(zip(times, prey)):
+        x = x_scale(t)
+        y = y_scale(p)
+        if i == 0:
+            ctx.moveTo(x, y)
+        else:
+            ctx.lineTo(x, y)
+    ctx.stroke()
+
+    # Draw predator line (red)
+    ctx.strokeStyle = "#ef4444"
+    ctx.lineWidth = 2
+    ctx.beginPath()
+    for i, (t, p) in enumerate(zip(times, predators)):
+        x = x_scale(t)
+        y = y_scale(p)
+        if i == 0:
+            ctx.moveTo(x, y)
+        else:
+            ctx.lineTo(x, y)
+    ctx.stroke()
+
+    # Draw legend
+    ctx.font = "14px system-ui"
+
+    ctx.fillStyle = "#3b82f6"
+    ctx.fillRect(width - 120, 20, 15, 15)
+    ctx.fillText(f"Prey: {int(prey[-1])}", width - 100, 32)
+
+    ctx.fillStyle = "#ef4444"
+    ctx.fillRect(width - 120, 45, 15, 15)
+    ctx.fillText(f"Predators: {int(predators[-1])}", width - 100, 57)
+
+    # Time display
+    ctx.fillStyle = "#94a3b8"
+    ctx.fillText(f"Time: {times[-1]:.1f}", padding + 10, padding + 20)
+
+
+def draw_phase_plot(data: dict, max_step: int):
+    """Draw phase space plot (predators vs prey)."""
+    phase_canvas = js.document.getElementById("phase-canvas")
+    phase_ctx = phase_canvas.getContext("2d")
+
+    width = phase_canvas.width
+    height = phase_canvas.height
+    padding = 50
+
+    # Clear
+    phase_ctx.fillStyle = "#1e293b"
+    phase_ctx.fillRect(0, 0, width, height)
+
+    if max_step < 2:
+        return
+
+    prey = data["prey"][:max_step]
+    predators = data["predators"][:max_step]
+
+    max_prey = max(prey) * 1.1
+    max_predators = max(predators) * 1.1
+
+    chart_width = width - 2 * padding
+    chart_height = height - 2 * padding
+
+    def x_scale(p):
+        return padding + (p / max_prey) * chart_width
+
+    def y_scale(p):
+        return height - padding - (p / max_predators) * chart_height
+
+    # Axes
+    phase_ctx.strokeStyle = "#64748b"
+    phase_ctx.lineWidth = 1
+    phase_ctx.beginPath()
+    phase_ctx.moveTo(padding, padding)
+    phase_ctx.lineTo(padding, height - padding)
+    phase_ctx.lineTo(width - padding, height - padding)
+    phase_ctx.stroke()
+
+    # Labels
+    phase_ctx.fillStyle = "#64748b"
+    phase_ctx.font = "12px system-ui"
+    phase_ctx.fillText("Prey Population", width // 2 - 40, height - 10)
+
+    phase_ctx.save()
+    phase_ctx.translate(15, height // 2 + 40)
+    phase_ctx.rotate(-3.14159 / 2)
+    phase_ctx.fillText("Predator Population", 0, 0)
+    phase_ctx.restore()
+
+    # Draw trajectory with gradient
+    phase_ctx.lineWidth = 2
+    for i in range(1, len(prey)):
+        # Gradient from purple to orange
+        progress = i / len(prey)
+        r = int(147 + (249 - 147) * progress)
+        g = int(51 + (115 - 51) * progress)
+        b = int(234 + (22 - 234) * progress)
+        phase_ctx.strokeStyle = f"rgb({r}, {g}, {b})"
+
+        phase_ctx.beginPath()
+        phase_ctx.moveTo(x_scale(prey[i-1]), y_scale(predators[i-1]))
+        phase_ctx.lineTo(x_scale(prey[i]), y_scale(predators[i]))
+        phase_ctx.stroke()
+
+    # Current point
+    if prey and predators:
+        phase_ctx.fillStyle = "#fbbf24"
+        phase_ctx.beginPath()
+        phase_ctx.arc(x_scale(prey[-1]), y_scale(predators[-1]), 6, 0, 6.28)
+        phase_ctx.fill()
+
+
+# ============================================================================
+# Animation Loop
+# ============================================================================
+
+def animate():
+    """Animation frame callback."""
+    global current_step, animation_frame, is_running
+
+    if not is_running or sim_data is None:
+        return
+
+    # Draw current state
+    draw_chart(sim_data, current_step)
+    draw_phase_plot(sim_data, current_step)
+
+    # Advance simulation
+    current_step += 5  # Speed: 5 steps per frame
+
+    if current_step >= len(sim_data["times"]):
+        current_step = len(sim_data["times"])
+        is_running = False
+        update_button_state()
+        return
+
+    animation_frame = js.window.requestAnimationFrame(animate)
+
+
+def start_simulation():
+    """Start or resume the simulation."""
+    global is_running, sim_data, current_step, params
+
+    if is_running:
+        return
+
+    # Read parameters from UI
+    params = SimulationParams()
+    params.initial_prey = int(js.document.getElementById("initial-prey").value)
+    params.initial_predators = int(js.document.getElementById("initial-predators").value)
+    params.prey_birth_rate = float(js.document.getElementById("birth-rate").value)
+    params.predation_rate = float(js.document.getElementById("predation-rate").value)
+    params.predator_death_rate = float(js.document.getElementById("death-rate").value)
+    params.conversion_rate = float(js.document.getElementById("conversion-rate").value)
+
+    # Run simulation
+    sim_data = run_simulation(params)
+    current_step = 0
+
+    is_running = True
+    update_button_state()
+    animate()
+
+
+def stop_simulation():
+    """Pause the simulation."""
+    global is_running, animation_frame
+
+    is_running = False
+    if animation_frame:
+        js.window.cancelAnimationFrame(animation_frame)
+    update_button_state()
+
+
+def reset_simulation():
+    """Reset the simulation."""
+    global is_running, current_step, sim_data, animation_frame
+
+    is_running = False
+    if animation_frame:
+        js.window.cancelAnimationFrame(animation_frame)
+
+    current_step = 0
+    sim_data = None
+
+    # Clear canvases
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, canvas.width, canvas.height)
+    draw_axes()
+
+    phase_ctx = js.document.getElementById("phase-canvas").getContext("2d")
+    phase_ctx.fillStyle = "#1e293b"
+    phase_ctx.fillRect(0, 0, canvas.width, canvas.height)
+
+    update_button_state()
+
+
+def update_button_state():
+    """Update button enabled/disabled states."""
+    start_btn = js.document.getElementById("start-btn")
+    stop_btn = js.document.getElementById("stop-btn")
+
+    if is_running:
+        start_btn.disabled = True
+        stop_btn.disabled = False
+    else:
+        start_btn.disabled = False
+        stop_btn.disabled = True
+
+
+# ============================================================================
+# Initialization
+# ============================================================================
+
+def init():
+    """Initialize the simulation."""
+    global canvas, ctx
+
+    canvas = js.document.getElementById("sim-canvas")
+    ctx = canvas.getContext("2d")
+
+    # Set canvas size
+    canvas.width = 600
+    canvas.height = 400
+
+    phase_canvas = js.document.getElementById("phase-canvas")
+    phase_canvas.width = 400
+    phase_canvas.height = 400
+
+    # Initial draw
+    ctx.fillStyle = "#1e293b"
+    ctx.fillRect(0, 0, canvas.width, canvas.height)
+    draw_axes()
+
+    # Button handlers
+    js.document.getElementById("start-btn").addEventListener("click", lambda e: start_simulation())
+    js.document.getElementById("stop-btn").addEventListener("click", lambda e: stop_simulation())
+    js.document.getElementById("reset-btn").addEventListener("click", lambda e: reset_simulation())
+
+    update_button_state()
+
+
+# Initialize on page load
+js.window.addEventListener("DOMContentLoaded", lambda e: init())
diff --git a/demos/validation-library/Makefile b/demos/validation-library/Makefile
new file mode 100644
index 0000000..576b6a7
--- /dev/null
+++ b/demos/validation-library/Makefile
@@ -0,0 +1,11 @@
+.PHONY: build serve clean
+
+build:
+	py2js src/validators.py -o dist/validators.js -s
+	py2js src/app.py -o dist/app.js -s -M src
+
+serve: build
+	python -m http.server 8001
+
+clean:
+	rm -rf dist/*.js dist/*.map
diff --git a/demos/validation-library/README.md b/demos/validation-library/README.md
new file mode 100644
index 0000000..09d744a
--- /dev/null
+++ b/demos/validation-library/README.md
@@ -0,0 +1,71 @@
+# Shared Validation Library Demo
+
+Write validation rules once in Python, use on both backend and frontend.
+
+## The Problem
+
+Teams often duplicate validation logic:
+- Python validation on the server (Django, FastAPI)
+- JavaScript validation on the client (React, Vue)
+
+This leads to bugs when rules diverge.
+
+## The Solution
+
+With Prescrypt, write validators **once** in Python:
+
+```python
+# validators.py - used by BOTH backend AND frontend
+
+def validate_email(email: str) -> ValidationResult:
+    if "@" not in email:
+        return ValidationResult.error("Email must contain @")
+    # ... more validation
+    return ValidationResult.ok()
+
+def validate_password(password: str) -> ValidationResult:
+    errors = []
+    if len(password) < 8:
+        errors.append("Password must be at least 8 characters")
+    # ... more checks
+    return ValidationResult.errors(errors) if errors else ValidationResult.ok()
+```
+
+## Features Demonstrated
+
+- **Email validation** with typo detection (`gmial.com` → "Did you mean gmail.com?")
+- **Password strength** meter with real-time feedback
+- **Credit card validation** using Luhn algorithm
+- **Phone number** validation with format normalization
+- **Composite validators** for entire forms
+
+## Build & Run
+
+```bash
+make build   # Compile to JavaScript
+make serve   # Start server on port 8001
+```
+
+Then open http://localhost:8001
+
+## Technical Highlights
+
+- Regex patterns work identically in Python and JavaScript
+- Classes with `@staticmethod` methods
+- Complex validation logic with early returns
+- Real-time UI feedback
+
+## Backend Integration
+
+The same `validators.py` can be imported in your Python backend:
+
+```python
+# Django view
+from shared.validators import validate_registration_form
+
+def register(request):
+    result = validate_registration_form(request.POST)
+    if not result.is_valid:
+        return JsonResponse({"errors": result.errors}, status=400)
+    # ... create user
+```
diff --git a/demos/validation-library/index.html b/demos/validation-library/index.html
new file mode 100644
index 0000000..2a8a9ee
--- /dev/null
+++ b/demos/validation-library/index.html
@@ -0,0 +1,355 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Shared Validation Library - Prescrypt Demo</title>
+    <style>
+        :root {
+            --primary: #6366f1;
+            --primary-dark: #4f46e5;
+            --success: #10b981;
+            --error: #ef4444;
+            --warning: #f59e0b;
+            --bg: #f8fafc;
+            --surface: #ffffff;
+            --text: #1e293b;
+            --text-muted: #64748b;
+            --border: #e2e8f0;
+        }
+
+        * {
+            box-sizing: border-box;
+            margin: 0;
+            padding: 0;
+        }
+
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+            background: var(--bg);
+            color: var(--text);
+            line-height: 1.6;
+            min-height: 100vh;
+        }
+
+        .container {
+            max-width: 600px;
+            margin: 0 auto;
+            padding: 40px 20px;
+        }
+
+        header {
+            text-align: center;
+            margin-bottom: 40px;
+        }
+
+        h1 {
+            font-size: 2rem;
+            color: var(--primary);
+            margin-bottom: 10px;
+        }
+
+        .subtitle {
+            color: var(--text-muted);
+            font-size: 1.1rem;
+        }
+
+        .highlight {
+            background: linear-gradient(135deg, var(--primary), var(--success));
+            -webkit-background-clip: text;
+            -webkit-text-fill-color: transparent;
+            background-clip: text;
+            font-weight: 600;
+        }
+
+        .card {
+            background: var(--surface);
+            border-radius: 16px;
+            box-shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
+            padding: 30px;
+            margin-bottom: 20px;
+        }
+
+        .card-header {
+            display: flex;
+            align-items: center;
+            gap: 10px;
+            margin-bottom: 25px;
+            padding-bottom: 15px;
+            border-bottom: 1px solid var(--border);
+        }
+
+        .card-icon {
+            width: 40px;
+            height: 40px;
+            background: var(--primary);
+            border-radius: 10px;
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            color: white;
+            font-size: 20px;
+        }
+
+        .card-title {
+            font-size: 1.25rem;
+            font-weight: 600;
+        }
+
+        .form-group {
+            margin-bottom: 20px;
+        }
+
+        label {
+            display: block;
+            font-weight: 500;
+            margin-bottom: 6px;
+            color: var(--text);
+        }
+
+        input {
+            width: 100%;
+            padding: 12px 16px;
+            font-size: 16px;
+            border: 2px solid var(--border);
+            border-radius: 10px;
+            outline: none;
+            transition: all 0.2s;
+            background: var(--surface);
+        }
+
+        input:focus {
+            border-color: var(--primary);
+            box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
+        }
+
+        input.valid {
+            border-color: var(--success);
+        }
+
+        input.invalid {
+            border-color: var(--error);
+        }
+
+        .feedback {
+            font-size: 13px;
+            margin-top: 6px;
+            min-height: 20px;
+        }
+
+        .feedback.error {
+            color: var(--error);
+        }
+
+        .feedback.success {
+            color: var(--success);
+        }
+
+        #password-strength {
+            display: none;
+            margin-top: 8px;
+        }
+
+        .strength-bar {
+            height: 6px;
+            background: var(--border);
+            border-radius: 3px;
+            overflow: hidden;
+        }
+
+        .meter {
+            height: 100%;
+            border-radius: 3px;
+            transition: all 0.3s;
+            text-align: center;
+            font-size: 10px;
+            font-weight: 600;
+            color: white;
+            line-height: 6px;
+        }
+
+        .meter.weak {
+            background: var(--error);
+        }
+
+        .meter.medium {
+            background: var(--warning);
+        }
+
+        .meter.strong {
+            background: var(--success);
+        }
+
+        .form-row {
+            display: grid;
+            grid-template-columns: 1fr 1fr;
+            gap: 15px;
+        }
+
+        button[type="submit"] {
+            width: 100%;
+            padding: 14px;
+            font-size: 16px;
+            font-weight: 600;
+            background: var(--primary);
+            color: white;
+            border: none;
+            border-radius: 10px;
+            cursor: pointer;
+            transition: all 0.2s;
+            margin-top: 10px;
+        }
+
+        button[type="submit"]:hover {
+            background: var(--primary-dark);
+            transform: translateY(-1px);
+        }
+
+        .form-result {
+            margin-top: 20px;
+            padding: 15px;
+            border-radius: 10px;
+            display: none;
+        }
+
+        .form-result.success {
+            display: block;
+            background: rgba(16, 185, 129, 0.1);
+            border: 1px solid var(--success);
+            color: var(--success);
+        }
+
+        .form-result.error {
+            display: block;
+            background: rgba(239, 68, 68, 0.1);
+            border: 1px solid var(--error);
+            color: var(--error);
+        }
+
+        .form-result ul {
+            margin: 10px 0 0 20px;
+        }
+
+        .info-box {
+            background: rgba(99, 102, 241, 0.1);
+            border: 1px solid var(--primary);
+            border-radius: 10px;
+            padding: 15px;
+            margin-top: 30px;
+        }
+
+        .info-box h3 {
+            color: var(--primary);
+            font-size: 14px;
+            text-transform: uppercase;
+            letter-spacing: 0.05em;
+            margin-bottom: 10px;
+        }
+
+        .info-box p {
+            color: var(--text-muted);
+            font-size: 14px;
+            margin-bottom: 8px;
+        }
+
+        .info-box code {
+            background: rgba(99, 102, 241, 0.2);
+            padding: 2px 6px;
+            border-radius: 4px;
+            font-size: 13px;
+        }
+
+        @media (max-width: 500px) {
+            .form-row {
+                grid-template-columns: 1fr;
+            }
+        }
+    </style>
+</head>
+<body>
+    <div class="container">
+        <header>
+            <h1>Shared Validation Library</h1>
+            <p class="subtitle">
+                Write validation rules <span class="highlight">once in Python</span>,
+                use on backend AND frontend
+            </p>
+        </header>
+
+        <div class="card">
+            <div class="card-header">
+                <div class="card-icon">📝</div>
+                <span class="card-title">Registration Form</span>
+            </div>
+
+            <form id="registration-form">
+                <div class="form-group">
+                    <label for="email">Email Address</label>
+                    <input type="text" id="email" placeholder="you@example.com" autocomplete="email">
+                    <div id="email-feedback" class="feedback"></div>
+                </div>
+
+                <div class="form-group">
+                    <label for="name">Full Name</label>
+                    <input type="text" id="name" placeholder="John Doe" autocomplete="name">
+                    <div id="name-feedback" class="feedback"></div>
+                </div>
+
+                <div class="form-group">
+                    <label for="password">Password</label>
+                    <input type="password" id="password" placeholder="••••••••">
+                    <div id="password-strength">
+                        <div class="strength-bar">
+                            <div id="strength-meter" class="meter"></div>
+                        </div>
+                    </div>
+                    <div id="password-feedback" class="feedback"></div>
+                </div>
+
+                <div class="form-group">
+                    <label for="confirm-password">Confirm Password</label>
+                    <input type="password" id="confirm-password" placeholder="••••••••">
+                    <div id="confirm-password-feedback" class="feedback"></div>
+                </div>
+
+                <div class="form-row">
+                    <div class="form-group">
+                        <label for="phone">Phone (optional)</label>
+                        <input type="tel" id="phone" placeholder="(555) 123-4567">
+                        <div id="phone-feedback" class="feedback"></div>
+                    </div>
+
+                    <div class="form-group">
+                        <label for="card">Card Number (optional)</label>
+                        <input type="text" id="card" placeholder="4242 4242 4242 4242">
+                        <div id="card-feedback" class="feedback"></div>
+                    </div>
+                </div>
+
+                <button type="submit">Create Account</button>
+
+                <div id="form-result" class="form-result"></div>
+            </form>
+
+            <div class="info-box">
+                <h3>How It Works</h3>
+                <p>
+                    The validation logic in <code>validators.py</code> runs in your browser
+                    as JavaScript, compiled by Prescrypt.
+                </p>
+                <p>
+                    The <strong>same Python code</strong> can run on your Django/FastAPI
+                    backend - eliminating duplicate validation logic!
+                </p>
+                <p>
+                    Try typing <code>test@gmial.com</code> to see typo detection, or
+                    <code>4242424242424242</code> for Luhn algorithm validation.
+                </p>
+            </div>
+        </div>
+    </div>
+
+    <script src="dist/validators.js"></script>
+    <script src="dist/app.js"></script>
+</body>
+</html>
diff --git a/demos/validation-library/src/app.py b/demos/validation-library/src/app.py
new file mode 100644
index 0000000..1477fef
--- /dev/null
+++ b/demos/validation-library/src/app.py
@@ -0,0 +1,247 @@
+"""Form Validation Demo
+
+Real-time form validation using shared validators.
+The same validation code runs on both server (Python) and client (JavaScript).
+"""
+from __future__ import annotations
+
+import js
+from validators import (
+    validate_email,
+    validate_password,
+    validate_password_match,
+    validate_required,
+    validate_min_length,
+    validate_phone,
+    validate_credit_card,
+    validate_registration_form,
+)
+
+
+# ============================================================================
+# UI Helpers
+# ============================================================================
+
+def show_validation(field_id: str, result):
+    """Show validation result for a field."""
+    field = js.document.getElementById(field_id)
+    feedback = js.document.getElementById(f"{field_id}-feedback")
+
+    if result.is_valid:
+        field.classList.remove("invalid")
+        field.classList.add("valid")
+        feedback.textContent = ""
+        feedback.className = "feedback"
+    else:
+        field.classList.remove("valid")
+        field.classList.add("invalid")
+        feedback.textContent = result.errors[0] if result.errors else "Invalid"
+        feedback.className = "feedback error"
+
+
+def clear_validation(field_id: str):
+    """Clear validation state for a field."""
+    field = js.document.getElementById(field_id)
+    feedback = js.document.getElementById(f"{field_id}-feedback")
+
+    field.classList.remove("valid", "invalid")
+    feedback.textContent = ""
+    feedback.className = "feedback"
+
+
+def show_password_strength(password: str):
+    """Show password strength indicator."""
+    strength_el = js.document.getElementById("password-strength")
+    meter_el = js.document.getElementById("strength-meter")
+
+    if not password:
+        strength_el.style.display = "none"
+        return
+
+    strength_el.style.display = "block"
+
+    # Calculate strength
+    score = 0
+    if len(password) >= 8:
+        score += 1
+    if len(password) >= 12:
+        score += 1
+    if any(c.isupper() for c in password):
+        score += 1
+    if any(c.islower() for c in password):
+        score += 1
+    if any(c.isdigit() for c in password):
+        score += 1
+    if any(c in "!@#$%^&*()_+-=[]{}|;:,.<>?" for c in password):
+        score += 1
+
+    # Update meter
+    percentage = (score / 6) * 100
+    meter_el.style.width = f"{percentage}%"
+
+    if score <= 2:
+        meter_el.className = "meter weak"
+        meter_el.textContent = "Weak"
+    elif score <= 4:
+        meter_el.className = "meter medium"
+        meter_el.textContent = "Medium"
+    else:
+        meter_el.className = "meter strong"
+        meter_el.textContent = "Strong"
+
+
+# ============================================================================
+# Field Validators
+# ============================================================================
+
+def validate_email_field(e):
+    """Validate email on input."""
+    value = e.target.value
+    if value:
+        result = validate_email(value)
+        show_validation("email", result)
+    else:
+        clear_validation("email")
+
+
+def validate_password_field(e):
+    """Validate password on input."""
+    value = e.target.value
+    show_password_strength(value)
+
+    if value:
+        result = validate_password(value)
+        show_validation("password", result)
+
+        # Also check confirmation if it has a value
+        confirm = js.document.getElementById("confirm-password").value
+        if confirm:
+            match_result = validate_password_match(value, confirm)
+            show_validation("confirm-password", match_result)
+    else:
+        clear_validation("password")
+
+
+def validate_confirm_field(e):
+    """Validate password confirmation on input."""
+    value = e.target.value
+    password = js.document.getElementById("password").value
+
+    if value:
+        result = validate_password_match(password, value)
+        show_validation("confirm-password", result)
+    else:
+        clear_validation("confirm-password")
+
+
+def validate_name_field(e):
+    """Validate name on input."""
+    value = e.target.value
+
+    if value:
+        result = validate_required(value, "Name")
+        if result.is_valid:
+            result = validate_min_length(value, 2, "Name")
+        show_validation("name", result)
+    else:
+        clear_validation("name")
+
+
+def validate_phone_field(e):
+    """Validate phone on input."""
+    value = e.target.value
+
+    if value:
+        result = validate_phone(value)
+        show_validation("phone", result)
+    else:
+        clear_validation("phone")
+
+
+def validate_card_field(e):
+    """Validate credit card on input."""
+    value = e.target.value
+
+    if value:
+        result = validate_credit_card(value)
+        show_validation("card", result)
+    else:
+        clear_validation("card")
+
+
+# ============================================================================
+# Form Submission
+# ============================================================================
+
+def handle_submit(e):
+    """Handle form submission."""
+    e.preventDefault()
+
+    # Gather form data
+    data = {
+        "email": js.document.getElementById("email").value,
+        "password": js.document.getElementById("password").value,
+        "confirm_password": js.document.getElementById("confirm-password").value,
+        "name": js.document.getElementById("name").value,
+    }
+
+    # Validate entire form
+    result = validate_registration_form(data)
+
+    # Show result
+    result_el = js.document.getElementById("form-result")
+
+    if result.is_valid:
+        result_el.className = "form-result success"
+        result_el.innerHTML = """
+            <strong>Success!</strong>
+            <p>All validations passed. In a real app, this would submit to the server.</p>
+            <p>The same validation code runs on both client and server!</p>
+        """
+    else:
+        errors_html = "<ul>" + "".join(f"<li>{err}</li>" for err in result.errors) + "</ul>"
+        result_el.className = "form-result error"
+        result_el.innerHTML = f"""
+            <strong>Validation Failed</strong>
+            {errors_html}
+        """
+
+
+# ============================================================================
+# Initialization
+# ============================================================================
+
+def init():
+    """Initialize the demo."""
+    # Email validation
+    email = js.document.getElementById("email")
+    email.addEventListener("input", validate_email_field)
+    email.addEventListener("blur", validate_email_field)
+
+    # Password validation
+    password = js.document.getElementById("password")
+    password.addEventListener("input", validate_password_field)
+
+    # Password confirmation
+    confirm = js.document.getElementById("confirm-password")
+    confirm.addEventListener("input", validate_confirm_field)
+
+    # Name validation
+    name = js.document.getElementById("name")
+    name.addEventListener("input", validate_name_field)
+
+    # Phone validation
+    phone = js.document.getElementById("phone")
+    phone.addEventListener("input", validate_phone_field)
+
+    # Card validation
+    card = js.document.getElementById("card")
+    card.addEventListener("input", validate_card_field)
+
+    # Form submission
+    form = js.document.getElementById("registration-form")
+    form.addEventListener("submit", handle_submit)
+
+
+# Initialize on page load
+js.window.addEventListener("DOMContentLoaded", lambda e: init())
diff --git a/demos/validation-library/src/validators.py b/demos/validation-library/src/validators.py
new file mode 100644
index 0000000..d3bcc59
--- /dev/null
+++ b/demos/validation-library/src/validators.py
@@ -0,0 +1,366 @@
+"""Shared Validation Library
+
+Write validation rules ONCE in Python, use on BOTH:
+- Django/FastAPI backend (Python)
+- Browser frontend (compiled to JavaScript)
+
+This eliminates the duplication of validation logic across frontend and backend.
+"""
+from __future__ import annotations
+
+import re
+
+
+# ============================================================================
+# Core Validation Result
+# ============================================================================
+
+class ValidationResult:
+    """Result of a validation check."""
+
+    def __init__(self, is_valid: bool, errors: list = None):
+        self.is_valid = is_valid
+        self.errors = errors or []
+
+    def __bool__(self):
+        return self.is_valid
+
+    @staticmethod
+    def ok():
+        return ValidationResult(True, [])
+
+    @staticmethod
+    def error(message: str):
+        return ValidationResult(False, [message])
+
+    @staticmethod
+    def errors(messages: list):
+        return ValidationResult(False, messages)
+
+    def merge(self, other):
+        """Merge two validation results."""
+        return ValidationResult(
+            self.is_valid and other.is_valid,
+            self.errors + other.errors
+        )
+
+
+# ============================================================================
+# String Validators
+# ============================================================================
+
+def validate_required(value: str, field_name: str = "Field") -> ValidationResult:
+    """Check that a value is not empty."""
+    if not value or not value.strip():
+        return ValidationResult.error(f"{field_name} is required")
+    return ValidationResult.ok()
+
+
+def validate_min_length(value: str, min_len: int, field_name: str = "Field") -> ValidationResult:
+    """Check minimum string length."""
+    if len(value) < min_len:
+        return ValidationResult.error(
+            f"{field_name} must be at least {min_len} characters"
+        )
+    return ValidationResult.ok()
+
+
+def validate_max_length(value: str, max_len: int, field_name: str = "Field") -> ValidationResult:
+    """Check maximum string length."""
+    if len(value) > max_len:
+        return ValidationResult.error(
+            f"{field_name} must be at most {max_len} characters"
+        )
+    return ValidationResult.ok()
+
+
+def validate_pattern(value: str, pattern: str, message: str) -> ValidationResult:
+    """Check that value matches a regex pattern."""
+    if not re.match(pattern, value):
+        return ValidationResult.error(message)
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Email Validation
+# ============================================================================
+
+EMAIL_PATTERN = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
+
+
+def validate_email(email: str) -> ValidationResult:
+    """Validate email address format."""
+    result = validate_required(email, "Email")
+    if not result:
+        return result
+
+    # Check basic format
+    if "@" not in email:
+        return ValidationResult.error("Email must contain @")
+
+    if not re.match(EMAIL_PATTERN, email):
+        return ValidationResult.error("Please enter a valid email address")
+
+    # Check for common typos
+    domain = email.split("@")[1].lower()
+    typo_domains = {
+        "gmial.com": "gmail.com",
+        "gmal.com": "gmail.com",
+        "gamil.com": "gmail.com",
+        "hotmal.com": "hotmail.com",
+        "yaho.com": "yahoo.com",
+    }
+    if domain in typo_domains:
+        suggestion = typo_domains[domain]
+        return ValidationResult.error(
+            f"Did you mean @{suggestion}?"
+        )
+
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Password Validation
+# ============================================================================
+
+def validate_password(password: str) -> ValidationResult:
+    """Validate password strength."""
+    errors = []
+
+    if len(password) < 8:
+        errors.append("Password must be at least 8 characters")
+
+    if not any(c.isupper() for c in password):
+        errors.append("Password must contain an uppercase letter")
+
+    if not any(c.islower() for c in password):
+        errors.append("Password must contain a lowercase letter")
+
+    if not any(c.isdigit() for c in password):
+        errors.append("Password must contain a number")
+
+    special_chars = "!@#$%^&*()_+-=[]{}|;:,.<>?"
+    if not any(c in special_chars for c in password):
+        errors.append("Password must contain a special character")
+
+    if errors:
+        return ValidationResult.errors(errors)
+    return ValidationResult.ok()
+
+
+def validate_password_match(password: str, confirm: str) -> ValidationResult:
+    """Check that passwords match."""
+    if password != confirm:
+        return ValidationResult.error("Passwords do not match")
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Number Validators
+# ============================================================================
+
+def validate_number_range(value, min_val=None, max_val=None, field_name: str = "Value") -> ValidationResult:
+    """Validate that a number is within a range."""
+    try:
+        num = float(value)
+    except (ValueError, TypeError):
+        return ValidationResult.error(f"{field_name} must be a number")
+
+    if min_val is not None and num < min_val:
+        return ValidationResult.error(f"{field_name} must be at least {min_val}")
+
+    if max_val is not None and num > max_val:
+        return ValidationResult.error(f"{field_name} must be at most {max_val}")
+
+    return ValidationResult.ok()
+
+
+def validate_integer(value, field_name: str = "Value") -> ValidationResult:
+    """Validate that a value is an integer."""
+    try:
+        num = float(value)
+        if num != int(num):
+            return ValidationResult.error(f"{field_name} must be a whole number")
+    except (ValueError, TypeError):
+        return ValidationResult.error(f"{field_name} must be a number")
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Phone Number Validation
+# ============================================================================
+
+def validate_phone(phone: str) -> ValidationResult:
+    """Validate phone number format."""
+    # Remove common formatting characters
+    cleaned = phone.replace(" ", "").replace("-", "").replace("(", "").replace(")", "").replace("+", "")
+
+    if not cleaned.isdigit():
+        return ValidationResult.error("Phone number must contain only digits")
+
+    if len(cleaned) < 10:
+        return ValidationResult.error("Phone number must be at least 10 digits")
+
+    if len(cleaned) > 15:
+        return ValidationResult.error("Phone number is too long")
+
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Credit Card Validation
+# ============================================================================
+
+def validate_credit_card(card_number: str) -> ValidationResult:
+    """Validate credit card number using Luhn algorithm."""
+    # Remove spaces and dashes
+    cleaned = card_number.replace(" ", "").replace("-", "")
+
+    if not cleaned.isdigit():
+        return ValidationResult.error("Card number must contain only digits")
+
+    if len(cleaned) < 13 or len(cleaned) > 19:
+        return ValidationResult.error("Invalid card number length")
+
+    # Luhn algorithm
+    digits = [int(d) for d in cleaned]
+    odd_digits = digits[-1::-2]
+    even_digits = digits[-2::-2]
+
+    checksum = sum(odd_digits)
+    for d in even_digits:
+        doubled = d * 2
+        if doubled > 9:
+            doubled -= 9
+        checksum += doubled
+
+    if checksum % 10 != 0:
+        return ValidationResult.error("Invalid card number")
+
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Date Validation
+# ============================================================================
+
+def validate_date_format(date_str: str, format_hint: str = "YYYY-MM-DD") -> ValidationResult:
+    """Validate date format (YYYY-MM-DD)."""
+    if not re.match(r"^\d{4}-\d{2}-\d{2}$", date_str):
+        return ValidationResult.error(f"Date must be in {format_hint} format")
+
+    parts = date_str.split("-")
+    year = int(parts[0])
+    month = int(parts[1])
+    day = int(parts[2])
+
+    if month < 1 or month > 12:
+        return ValidationResult.error("Invalid month")
+
+    days_in_month = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+    # Leap year check
+    is_leap = (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
+    if is_leap and month == 2:
+        max_day = 29
+    else:
+        max_day = days_in_month[month - 1]
+
+    if day < 1 or day > max_day:
+        return ValidationResult.error("Invalid day for this month")
+
+    return ValidationResult.ok()
+
+
+def validate_age(birth_date: str, min_age: int = 0, max_age: int = 150) -> ValidationResult:
+    """Validate age based on birth date."""
+    result = validate_date_format(birth_date)
+    if not result:
+        return result
+
+    parts = birth_date.split("-")
+    birth_year = int(parts[0])
+
+    # Approximate age calculation (good enough for validation)
+    current_year = 2024  # In real code, use actual current year
+    age = current_year - birth_year
+
+    if age < min_age:
+        return ValidationResult.error(f"Must be at least {min_age} years old")
+
+    if age > max_age:
+        return ValidationResult.error("Invalid birth date")
+
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Composite Validators - Registration Form
+# ============================================================================
+
+def validate_registration_form(data: dict) -> ValidationResult:
+    """Validate a complete registration form."""
+    errors = []
+
+    # Email
+    email_result = validate_email(data.get("email", ""))
+    errors.extend(email_result.errors)
+
+    # Password
+    password_result = validate_password(data.get("password", ""))
+    errors.extend(password_result.errors)
+
+    # Password confirmation
+    if data.get("password"):
+        match_result = validate_password_match(
+            data.get("password", ""),
+            data.get("confirm_password", "")
+        )
+        errors.extend(match_result.errors)
+
+    # Name
+    name = data.get("name", "")
+    name_result = validate_required(name, "Name")
+    if name_result:
+        name_result = validate_min_length(name, 2, "Name")
+    errors.extend(name_result.errors if not name_result.is_valid else [])
+
+    # Age (optional)
+    if data.get("birth_date"):
+        age_result = validate_age(data["birth_date"], min_age=13)
+        errors.extend(age_result.errors)
+
+    if errors:
+        return ValidationResult.errors(errors)
+    return ValidationResult.ok()
+
+
+# ============================================================================
+# Composite Validators - Order Form
+# ============================================================================
+
+def validate_order(items: list, total: float, user_balance: float = None) -> ValidationResult:
+    """Validate an order."""
+    errors = []
+
+    if not items:
+        errors.append("Order must contain at least one item")
+
+    if total <= 0:
+        errors.append("Order total must be positive")
+
+    # Validate each item
+    for i in range(len(items)):
+        item = items[i]
+        if item.get("quantity", 0) <= 0:
+            errors.append(f"Item {i+1}: quantity must be positive")
+        if item.get("price", 0) < 0:
+            errors.append(f"Item {i+1}: price cannot be negative")
+
+    # Check user balance if provided
+    if user_balance is not None and total > user_balance:
+        errors.append(f"Insufficient balance (need ${total:.2f}, have ${user_balance:.2f})")
+
+    if errors:
+        return ValidationResult.errors(errors)
+    return ValidationResult.ok()
diff --git a/docs/guide/cheat-sheet.md b/docs/guide/cheat-sheet.md
new file mode 100644
index 0000000..e8d7ab6
--- /dev/null
+++ b/docs/guide/cheat-sheet.md
@@ -0,0 +1,363 @@
+# Prescrypt Cheat Sheet
+
+A quick reference for Python developers writing JavaScript applications with Prescrypt.
+
+---
+
+## Quick Start
+
+```bash
+# Compile Python to JavaScript
+py2js myapp.py -o myapp.js
+
+# With source maps (for debugging)
+py2js myapp.py -o myapp.js -s
+
+# Include full stdlib (no tree-shaking)
+py2js myapp.py -o myapp.js -m
+```
+
+---
+
+## JavaScript Interop
+
+Access JavaScript globals via the `js` module:
+
+```python
+import js
+
+# DOM manipulation
+el = js.document.getElementById("myid")
+el.textContent = "Hello"
+el.classList.add("active")
+
+# Window and console
+js.console.log("Debug message")
+js.window.alert("Hello!")
+
+# Timers
+js.setTimeout(lambda: print("delayed"), 1000)
+
+# JSON
+data = js.JSON.parse('{"x": 1}')
+text = js.JSON.stringify({"x": 1})
+```
+
+### Creating JavaScript Objects
+
+```python
+# Use js.eval for object literals (Object.new() doesn't work)
+options = js.eval("({method: 'POST', headers: {}})")
+options.body = "data"
+
+# Access object properties
+value = obj.property      # obj.property
+value = obj["key"]        # obj["key"]
+```
+
+### Fetch API
+
+```python
+def on_response(response):
+    response.text().then(handle_text)
+
+def handle_text(text):
+    data = js.JSON.parse(text)
+    print(data.message)
+
+options = js.eval("({method: 'POST', headers: {'Content-Type': 'application/json'}})")
+options.body = js.JSON.stringify({"key": "value"})
+js.fetch("/api/endpoint", options).then(on_response)
+```
+
+### Event Handlers
+
+```python
+def handle_click(event):
+    event.preventDefault()
+    print("Clicked:", event.target.id)
+
+btn = js.document.getElementById("my-btn")
+btn.addEventListener("click", handle_click)
+
+# Factory pattern for closures
+def make_handler(value):
+    def handler(e):
+        print("Value:", value)
+    return handler
+
+btn.addEventListener("click", make_handler(42))
+```
+
+---
+
+## Supported Python Features
+
+### Classes
+
+```python
+class Animal:
+    def __init__(self, name):
+        self.name = name
+
+    def speak(self):
+        return self.name + " makes a sound"
+
+class Dog(Animal):
+    def __init__(self, name):
+        super().__init__(name)  # super() works
+
+    def speak(self):
+        return self.name + " barks"
+
+# Decorators
+class MyClass:
+    @staticmethod
+    def static_method(x):
+        return x * 2
+
+    @classmethod
+    def class_method(cls, x):
+        return cls(x)
+
+    @property
+    def value(self):
+        return self._value
+
+    @value.setter
+    def value(self, v):
+        self._value = v
+```
+
+### Comprehensions
+
+```python
+squares = [x * x for x in range(10)]
+evens = [x for x in range(20) if x % 2 == 0]
+doubled = {k: v * 2 for k in d}  # dict comprehension
+```
+
+### Async/Await
+
+```python
+async def fetch_data(url):
+    response = await js.fetch(url)
+    data = await response.json()
+    return data
+```
+
+### Generators
+
+```python
+def countdown(n):
+    while n > 0:
+        yield n
+        n -= 1
+
+for x in countdown(5):
+    print(x)
+```
+
+### Context Managers
+
+```python
+class MyContext:
+    def __enter__(self):
+        print("entering")
+        return self
+
+    def __exit__(self, *args):
+        print("exiting")
+
+with MyContext() as ctx:
+    print("inside")
+```
+
+### Lambdas with Defaults
+
+```python
+add = lambda x, y=1: x + y
+```
+
+---
+
+## What Doesn't Work (Workarounds)
+
+### Tuple Unpacking
+
+```python
+# NOT SUPPORTED
+a, b = get_pair()
+for k, v in dict.items():
+for i, x in enumerate(lst):
+
+# WORKAROUND: Use indexing
+result = get_pair()
+a = result[0]
+b = result[1]
+
+for k in my_dict:
+    v = my_dict[k]
+
+for i in range(len(lst)):
+    x = lst[i]
+```
+
+### F-String Format Specifiers
+
+```python
+# NOT SUPPORTED (compiler hangs or wrong output)
+f"{x:,}"      # thousands separator
+f"{x:.2f}"    # fixed precision
+f"{x:>10}"    # width/alignment
+
+# WORKAROUND: Use str() and string methods
+str(int(x))              # instead of f"{x:.0f}"
+str(round(x, 2))         # instead of f"{x:.2f}"
+str(x).rjust(10)         # instead of f"{x:>10}"
+```
+
+### Variable Scoping in Loops
+
+```python
+# PROBLEM: Variables reused across loops cause strict mode errors
+for x in list1:
+    print(x)
+for x in list2:  # Error: x already declared
+    print(x)
+
+# WORKAROUND: Use unique variable names
+for x1 in list1:
+    print(x1)
+for x2 in list2:
+    print(x2)
+```
+
+### Variables First Assigned in Conditionals
+
+```python
+# PROBLEM: Variable not declared before conditional
+if condition:
+    result = "yes"
+else:
+    result = "no"  # Error: assignment to undeclared variable
+
+# WORKAROUND: Declare before conditional
+result = None
+if condition:
+    result = "yes"
+else:
+    result = "no"
+```
+
+### Chained Assignment with Subscripts
+
+```python
+# NOT SUPPORTED
+a[0] = a[1] = False
+
+# WORKAROUND: Split into separate statements
+a[0] = False
+a[1] = False
+```
+
+### dict.get() with Default
+
+```python
+# May not work as expected
+value = d.get("key", default)
+
+# WORKAROUND: Use explicit check
+if "key" in d:
+    value = d["key"]
+else:
+    value = default
+```
+
+### Generator Expressions in Builtins
+
+```python
+# May not work
+total = sum(x["value"] for x in data)
+
+# WORKAROUND: Use explicit loop
+total = 0
+for x in data:
+    total += x["value"]
+```
+
+---
+
+## JavaScript Differences
+
+| Python | JavaScript (Prescrypt) |
+|--------|------------------------|
+| `4.0` | `4` (no float distinction) |
+| `100/0` → ZeroDivisionError | `Infinity` |
+| `print(end="")` | Always adds newline |
+| `None` | `null` |
+| `True`/`False` | `true`/`false` |
+
+---
+
+## Standard Library
+
+Supported builtins: `print`, `len`, `range`, `enumerate`, `zip`, `map`, `filter`, `sorted`, `reversed`, `sum`, `min`, `max`, `abs`, `round`, `int`, `float`, `str`, `bool`, `list`, `dict`, `set`, `tuple`, `isinstance`, `hasattr`, `getattr`, `setattr`
+
+String methods: Most common methods work (`split`, `join`, `strip`, `replace`, `startswith`, `endswith`, `upper`, `lower`, `count`, `find`, `index`, etc.)
+
+List methods: `append`, `extend`, `insert`, `remove`, `pop`, `clear`, `index`, `count`, `sort`, `reverse`, `copy`
+
+Dict methods: `keys`, `values`, `items`, `get`, `pop`, `update`, `clear`, `copy`
+
+---
+
+## Project Structure Example
+
+```
+my-project/
+├── src/
+│   └── app.py          # Python source
+├── dist/
+│   └── app.js          # Compiled JavaScript
+├── index.html          # HTML that loads app.js
+└── Makefile
+```
+
+```makefile
+build:
+	py2js src/app.py -o dist/app.js -s
+
+serve: build
+	python -m http.server 8000
+
+clean:
+	rm -rf dist/*.js dist/*.map
+```
+
+```html
+<!DOCTYPE html>
+<html>
+<head>
+    <title>My App</title>
+</head>
+<body>
+    <div id="app"></div>
+    <script src="dist/app.js"></script>
+</body>
+</html>
+```
+
+---
+
+## Tips
+
+1. **Test incrementally**: Compile and test small pieces of code to catch unsupported patterns early.
+
+2. **Check browser console**: Runtime errors appear in the browser's developer console.
+
+3. **Use source maps**: The `-s` flag generates source maps for easier debugging.
+
+4. **Avoid Python-isms**: Stick to simple patterns; avoid (for now) advanced unpacking, walrus operator, match statements.
+
+5. **JS objects vs Python dicts**: When working with JS APIs, results are JS objects (use `.property`), not Python dicts (no `.get()` method).
diff --git a/git-town.toml b/git-town.toml
new file mode 100644
index 0000000..c596169
--- /dev/null
+++ b/git-town.toml
@@ -0,0 +1,8 @@
+# See https://www.git-town.com/configuration-file for details
+
+[branches]
+main = "main"
+
+[hosting]
+dev-remote = "origin"
+github-connector = "api"
diff --git a/mkdocs.yml b/mkdocs.yml
index 8ab2ad1..8688bfd 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -99,6 +99,7 @@ nav:
       - Source Maps: guide/source-maps.md
       - Optimization: guide/optimization.md
       - Troubleshooting: guide/troubleshooting.md
+      - Cheat Sheet: guide/cheat-sheet.md
   - Examples:
       - examples/index.md
       - Browser App: examples/browser-app.md
diff --git a/notes/TODO.md b/notes/TODO.md
index 16d50ca..441916a 100644
--- a/notes/TODO.md
+++ b/notes/TODO.md
@@ -1,6 +1,6 @@
 # Prescrypt TODO
 
-**Current Status:** v0.9.1 (released) | **Tests:** 2409 (2381 passing, 28 skipped) | **Coverage:** 89%
+**Current Status:** v0.9.2 (in progress) | **Tests:** 2385 passing, 28 skipped | **Coverage:** 89%
 
 See `notes/history.md` for completed work (Stages 0-6).
 
@@ -35,56 +35,66 @@ See `notes/history.md` for completed work (Stages 0-6).
 - [x] `__all__` to control module exports
 - [x] Context manager protocol (`__enter__`/`__exit__`)
 
+### Class System Enhancements (v0.9.2) ✓
+- [x] `super()` support with `super_proxy` runtime
+- [x] `@staticmethod` and `@classmethod` decorators
+- [x] `@property` decorator with getter/setter/deleter
+- [x] Special method dispatch (`__eq__`, `__lt__`, `__gt__`, `__le__`, `__ge__`)
+- [x] Container special methods (`__getitem__`, `__setitem__`, `__delitem__`)
+
 ---
 
-## Future Enhancements
+## Missing Features (discovered via demos)
 
-- [ ] Dataclasses and/or attrs support
-- [ ] `__slots__` support
-- [ ] Multiple inheritance (MRO)
-- [ ] `match` statement (structural pattern matching)
-- [ ] Watch mode for CLI
+### Tuple Unpacking ✓
 
----
+These patterns now work:
+
+- [x] **Assignment unpacking:** `a, b = func()`
+- [x] **For loop unpacking:** `for k, v in dict.items()`
+- [x] **Enumerate unpacking:** `for i, x in enumerate(lst)`
+- [x] **Nested unpacking:** `for i, (k, v) in enumerate(d.items())`
+- [x] **Chained assignment with subscripts:** `a[0] = a[1] = False` (fixed in v0.9.2)
+
+### F-String Format Specifiers ✓
 
-## Class System Enhancements
+These format specifiers now work:
 
-**Goal:** Full class support with decorators and special methods.
+- [x] **Thousands separator:** `f"{x:,}"` → outputs `"1,234,567"`
+- [x] **Fixed precision:** `f"{x:.2f}"` → outputs `"3.14"`
+- [x] **Width/alignment:** `f"{x:>10}"` → outputs `"        42"`
+- [x] **Combined:** `f"{x:,.2f}"` → outputs `"1,234,567.89"`
 
-### Phase 1: `super()` Support
-- [ ] Detect `super` as special function in `gen_call_named()`
-- [ ] Generate `this._base_class.METHOD.call(this, args)`
-- [ ] Enable test: `class_super.py`
+### Variable Scoping (Low Priority)
 
-### Phase 2: `@staticmethod` / `@classmethod`
-- [ ] Remove "Class decorators not supported" error
-- [ ] Handle `@staticmethod` - no `this` binding
-- [ ] Handle `@classmethod` - pass constructor as `cls`
-- [ ] Enable test: `class_staticclassmethod.py`
+- [ ] **Loop variable redeclaration:** Variables declared in one loop aren't re-declared in subsequent loops with the same name, causing strict mode errors. Workaround: use different variable names.
 
-### Phase 3: `@property` Decorator
-- [ ] Detect `@property` and `.setter`/`.deleter`
-- [ ] Generate `Object.defineProperty()` calls
-- [ ] Enable test: `builtin_property.py`
+### Recently Fixed
 
-### Phase 4: Special Method Dispatch
-- [ ] `__getitem__` / `__setitem__` dispatch
-- [ ] `__len__` in `len()` calls
-- [ ] `__eq__` in equality comparisons
-- [ ] Enable tests: `class_binop.py`, `getitem.py`
+- [x] **Class `var` declaration:** Classes weren't declared with `var`, causing "assignment to undeclared variable" in strict mode. Fixed in `codegen/_statements/classes.py`.
+
+## Future Enhancements
+
+- [ ] Dataclasses support
+- [ ] `__slots__` support
+- [ ] Multiple inheritance (MRO)
+- [ ] `match` statement (structural pattern matching)
+- [ ] Watch mode for CLI
 
 ---
 
-## Demos & Use Cases
+## Demos & Use Cases ✓
+
+Demos created in `demos/` directory:
 
-Develop demos for various use cases:
+1. [x] **python-playground** - Interactive Python learning (server-side compilation)
+2. [x] **validation-library** - Shared validation (backend + frontend)
+3. [x] **data-dashboard** - Sales analytics with Canvas charts
+4. [x] **browser-extension** - Chrome/Firefox page analyzer
+5. [x] **simulation** - Predator-prey Lotka-Volterra model
+6. [x] **edge-worker** - Cloudflare Workers (bot detection, A/B testing)
 
-1. Interactive Python learning platforms
-2. Shared validation libraries (backend + frontend)
-3. Lightweight data dashboards
-4. Browser extensions in Python
-5. Scientific simulations / educational widgets
-6. Edge computing (Cloudflare Workers)
+See `demos/README.md` for documentation.
 
 ---
 
diff --git a/noxfile.py b/noxfile.py
index f5bb1bd..39aee1c 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -11,8 +11,8 @@ def tests(session: nox.Session):
     session.run("pytest")
 
 
-@nox.session(python=PYTHONS[0])
-def lint(session: nox.Session):
+@nox.session
+def check(session: nox.Session):
     uv_sync(session)
     session.run("ruff", "check")
 
@@ -22,5 +22,10 @@ def lint(session: nox.Session):
 #
 def uv_sync(session: nox.Session):
     session.run(
-        "uv", "sync", "-q", "--all-groups", "--all-extras", "--active", external=True
+        # "uv", "sync", "-q", "--all-groups", "--all-extras", "--active", external=True
+        "uv",
+        "sync",
+        "-q",
+        "--active",
+        external=True,
     )
diff --git a/programs/internal/chained_assignment.py b/programs/internal/chained_assignment.py
new file mode 100644
index 0000000..57b4ee1
--- /dev/null
+++ b/programs/internal/chained_assignment.py
@@ -0,0 +1,116 @@
+"""Test chained assignment with subscripts and attributes.
+
+This showcases the ability to use multiple assignment targets including
+array indices and object attributes, not just simple variable names.
+
+Example: a[0] = a[1] = value assigns value to both a[0] and a[1]
+"""
+from __future__ import annotations
+
+
+# ============================================================================
+# Chained Assignment with List Subscripts
+# ============================================================================
+
+print("=== Chained Subscript Assignment ===")
+
+# Basic chained subscript assignment
+a = [True, True]
+a[0] = a[1] = False
+print(f"a[0]={str(a[0])}, a[1]={str(a[1])}")
+
+# Triple subscript assignment
+b = [0, 0, 0]
+b[0] = b[1] = b[2] = 42
+print(f"b[0]={b[0]}, b[1]={b[1]}, b[2]={b[2]}")
+
+# Mixed indices
+c = [1, 2, 3, 4, 5]
+c[0] = c[4] = 99
+print(f"c[0]={c[0]}, c[2]={c[2]}, c[4]={c[4]}")
+
+
+# ============================================================================
+# Chained Assignment with Dict Subscripts
+# ============================================================================
+
+print("\n=== Chained Dict Assignment ===")
+
+# Dict subscript assignment
+d = {}
+d["x"] = d["y"] = 10
+print(f'd["x"]={d["x"]}, d["y"]={d["y"]}')
+
+# Mixed string keys
+e = {}
+e["name"] = e["alias"] = "Python"
+print(f'e["name"]={e["name"]}, e["alias"]={e["alias"]}')
+
+
+# ============================================================================
+# Chained Assignment with Attributes
+# ============================================================================
+
+print("\n=== Chained Attribute Assignment ===")
+
+class Point:
+    def __init__(self):
+        self.x = 0
+        self.y = 0
+        self.z = 0
+
+p = Point()
+p.x = p.y = 5
+print(f"p.x={p.x}, p.y={p.y}")
+
+# Triple attribute assignment
+q = Point()
+q.x = q.y = q.z = 100
+print(f"q.x={q.x}, q.y={q.y}, q.z={q.z}")
+
+
+# ============================================================================
+# Mixed Chained Assignment (Names, Subscripts, Attributes)
+# ============================================================================
+
+print("\n=== Mixed Chained Assignment ===")
+
+class Container:
+    def __init__(self):
+        self.value = 0
+
+container = Container()
+arr = [0]
+result = arr[0] = container.value = 77
+print(f"result={result}")
+print(f"arr[0]={arr[0]}")
+print(f"container.value={container.value}")
+
+
+# ============================================================================
+# Edge Cases
+# ============================================================================
+
+print("\n=== Edge Cases ===")
+
+# Nested subscript - assigning to multiple positions
+matrix = [[0, 0], [0, 0]]
+matrix[0][0] = matrix[1][1] = 1
+print(f"matrix[0][0]={matrix[0][0]}, matrix[0][1]={matrix[0][1]}")
+print(f"matrix[1][0]={matrix[1][0]}, matrix[1][1]={matrix[1][1]}")
+
+# Boolean values
+flags = [True, True, True]
+flags[0] = flags[1] = flags[2] = False
+all_false = flags[0] == False and flags[1] == False and flags[2] == False
+print(f"All flags false: {str(all_false)}")
+
+# String values in dict
+config = {}
+config["host"] = config["backup_host"] = "localhost"
+print(f'config["host"]={config["host"]}')
+print(f'config["backup_host"]={config["backup_host"]}')
+
+# Verify all assignments are correct
+print("\n=== Verification ===")
+print("All tests passed: True")
diff --git a/programs/internal/class_property.py b/programs/internal/class_property.py
new file mode 100644
index 0000000..1030379
--- /dev/null
+++ b/programs/internal/class_property.py
@@ -0,0 +1,101 @@
+"""Test @property decorator."""
+from __future__ import annotations
+
+
+# Basic property with getter only
+class Point:
+    def __init__(self, x, y):
+        self._x = x
+        self._y = y
+
+    @property
+    def x(self):
+        print("get x")
+        return self._x
+
+    @property
+    def y(self):
+        print("get y")
+        return self._y
+
+
+p = Point(1, 2)
+print(p.x)
+print(p.y)
+
+
+# Property with getter and setter
+class Temperature:
+    def __init__(self, celsius):
+        self._celsius = celsius
+
+    @property
+    def celsius(self):
+        print("get celsius")
+        return self._celsius
+
+    @celsius.setter
+    def celsius(self, value):
+        print("set celsius")
+        self._celsius = value
+
+    @property
+    def fahrenheit(self):
+        return self._celsius * 9 // 5 + 32  # Use integer division
+
+
+t = Temperature(0)
+print(t.celsius)
+t.celsius = 100
+print(t.celsius)
+print(t.fahrenheit)
+
+
+# Property with getter, setter, and deleter
+class Container:
+    def __init__(self, value):
+        self._value = value
+
+    @property
+    def value(self):
+        print("get value")
+        return self._value
+
+    @value.setter
+    def value(self, val):
+        print("set value")
+        self._value = val
+
+    @value.deleter
+    def value(self):
+        print("del value")
+        self._value = None
+
+
+c = Container(42)
+print(c.value)
+c.value = 100
+print(c.value)
+del c.value
+print(c.value)
+
+
+# Read-only property (no setter) - should raise AttributeError
+class ReadOnly:
+    def __init__(self):
+        self._data = "secret"
+
+    @property
+    def data(self):
+        return self._data
+
+
+ro = ReadOnly()
+print(ro.data)
+try:
+    ro.data = "hacked"
+except AttributeError:
+    print("AttributeError: can't set")
+
+
+print("class_property tests done")
diff --git a/programs/internal/class_special_methods.py b/programs/internal/class_special_methods.py
new file mode 100644
index 0000000..e769158
--- /dev/null
+++ b/programs/internal/class_special_methods.py
@@ -0,0 +1,71 @@
+"""Test special method dispatch for classes."""
+from __future__ import annotations
+
+
+# Test comparison operators
+class MyNumber:
+    def __init__(self, value):
+        self.value = value
+
+    def __eq__(self, other):
+        print("eq")
+        return self.value == other.value
+
+    def __lt__(self, other):
+        print("lt")
+        return self.value < other.value
+
+    def __gt__(self, other):
+        print("gt")
+        return self.value > other.value
+
+    def __le__(self, other):
+        print("le")
+        return self.value <= other.value
+
+    def __ge__(self, other):
+        print("ge")
+        return self.value >= other.value
+
+
+n1 = MyNumber(5)
+n2 = MyNumber(10)
+n3 = MyNumber(5)
+
+print(n1 == n2)
+print(n1 == n3)
+print(n1 < n2)
+print(n1 > n2)
+print(n1 <= n3)
+print(n1 >= n3)
+
+
+# Test container special methods
+class Container:
+    def __init__(self):
+        self._data = {}
+
+    def __getitem__(self, key):
+        print(f"getitem {key}")
+        return self._data.get(key, None)
+
+    def __setitem__(self, key, value):
+        print(f"setitem {key}={value}")
+        self._data[key] = value
+
+    def __delitem__(self, key):
+        print(f"delitem {key}")
+        if key in self._data:
+            del self._data[key]
+
+
+c = Container()
+c["a"] = 1
+c["b"] = 2
+print(c["a"])
+print(c["b"])
+del c["a"]
+print(c["a"])
+
+
+print("special_methods tests done")
diff --git a/programs/internal/class_staticclassmethod.py b/programs/internal/class_staticclassmethod.py
new file mode 100644
index 0000000..81e2e1e
--- /dev/null
+++ b/programs/internal/class_staticclassmethod.py
@@ -0,0 +1,80 @@
+"""Test @staticmethod and @classmethod decorators."""
+from __future__ import annotations
+
+
+class Calculator:
+    value = 100
+
+    @staticmethod
+    def add(a, b):
+        return a + b
+
+    @staticmethod
+    def multiply(a, b):
+        return a * b
+
+    @classmethod
+    def get_value(cls):
+        return cls.value
+
+    @classmethod
+    def create_with_value(cls, val):
+        cls.value = val
+        return cls()
+
+    # Test with 'self' as first param (MicroPython style)
+    @classmethod
+    def get_value_self(self):
+        return self.value
+
+
+# Test staticmethod from class
+print(Calculator.add(1, 2))
+print(Calculator.multiply(3, 4))
+
+# Test staticmethod from instance
+calc = Calculator()
+print(calc.add(5, 6))
+print(calc.multiply(7, 8))
+
+# Test classmethod from class
+print(Calculator.get_value())
+
+# Test classmethod from instance
+print(calc.get_value())
+
+# Test classmethod with 'self' param name
+print(calc.get_value_self())
+
+
+# Test that staticmethod doesn't bind 'this'
+class Counter:
+    count = 0
+
+    @staticmethod
+    def increment():
+        Counter.count += 1
+        return Counter.count
+
+
+print(Counter.increment())
+print(Counter.increment())
+c = Counter()
+print(c.increment())
+
+
+# Test classmethod returning instance
+class Factory:
+    @classmethod
+    def create(cls):
+        return cls()
+
+    def describe(self):
+        return "Factory instance"
+
+
+f = Factory.create()
+print(f.describe())
+
+
+print("class_staticclassmethod tests done")
diff --git a/programs/internal/class_super.py b/programs/internal/class_super.py
new file mode 100644
index 0000000..4c51f5a
--- /dev/null
+++ b/programs/internal/class_super.py
@@ -0,0 +1,91 @@
+"""Test super() functionality."""
+from __future__ import annotations
+
+
+# Basic super() call
+class Base:
+    def __init__(self):
+        self.a = 1
+
+    def meth(self):
+        print("Base.meth", self.a)
+        return self.a
+
+
+class Sub(Base):
+    def meth(self):
+        print("Sub.meth")
+        return super().meth()
+
+
+s = Sub()
+print(s.meth())
+
+
+# super() attribute access
+class A:
+    x = 42
+
+
+class B(A):
+    def get_x(self):
+        return super().x
+
+
+print(B().get_x())
+
+
+# Method chaining with super()
+class C:
+    def foo(self):
+        return [1, 2, 3]
+
+
+class D(C):
+    def bar(self):
+        return super().foo()[1]
+
+
+print(D().bar())
+
+
+# super() string representation (first 18 chars)
+class E:
+    def p(self):
+        print(str(super())[:18])
+
+
+E().p()
+
+
+# super().__init__() when inheriting from object
+class F:
+    def __init__(self):
+        super().__init__()
+        print("F.__init__")
+
+
+F()
+
+
+# Set/delete on super raises AttributeError
+class G:
+    pass
+
+
+class H(G):
+    def test(self):
+        try:
+            super().x = 1
+        except AttributeError:
+            print("AttributeError on set")
+        try:
+            del super().x
+        except AttributeError:
+            print("AttributeError on del")
+
+
+H().test()
+
+
+print("class_super tests done")
diff --git a/programs/internal/fstring_formatting.py b/programs/internal/fstring_formatting.py
new file mode 100644
index 0000000..ef1a4f3
--- /dev/null
+++ b/programs/internal/fstring_formatting.py
@@ -0,0 +1,173 @@
+"""Test f-string format specifiers.
+
+This showcases the f-string formatting capabilities including:
+- Thousands separator (:,)
+- Width and alignment (<, >, ^)
+- Custom fill characters
+- Zero padding
+- Precision for floats
+- Combined format specifiers
+"""
+from __future__ import annotations
+
+
+# ============================================================================
+# Thousands Separator
+# ============================================================================
+
+print("=== Thousands Separator ===")
+
+# Basic thousands separator
+big_num = 1234567
+print(f"1234567 with commas: {big_num:,}")
+
+# Larger number
+million = 1000000
+print(f"One million: {million:,}")
+
+# Billions
+billion = 1234567890
+print(f"Billion: {billion:,}")
+
+# Small number (no commas needed)
+small = 123
+print(f"123 with commas: {small:,}")
+
+# Zero
+zero = 0
+print(f"Zero with commas: {zero:,}")
+
+# Negative number
+negative = -9876543
+print(f"Negative: {negative:,}")
+
+
+# ============================================================================
+# Thousands with Float Precision
+# ============================================================================
+
+print("\n=== Thousands + Precision ===")
+
+# Float with thousands and precision
+price = 1234567.89
+print(f"Price: {price:,.2f}")
+
+# Large money amount
+salary = 150000.5
+print(f"Salary: {salary:,.2f}")
+
+# Percentage (small)
+rate = 1234.567
+print(f"Rate: {rate:,.1f}")
+
+
+# ============================================================================
+# Width and Alignment
+# ============================================================================
+
+print("\n=== Width and Alignment ===")
+
+# Right align (default for numbers)
+val = 42
+print(f"Right align :>10 : '{val:>10}'")
+
+# Left align
+name = "hi"
+print(f"Left align  :<10 : '{name:<10}'")
+
+# Center align
+mid = "X"
+print(f"Center      :^10 : '{mid:^10}'")
+
+# Number alignment
+for i in [1, 12, 123, 1234]:
+    print(f"  {i:>6}")
+
+
+# ============================================================================
+# Custom Fill Characters
+# ============================================================================
+
+print("\n=== Custom Fill Characters ===")
+
+# Star fill
+num = 42
+print(f"Star fill   :*>8 : '{num:*>8}'")
+
+# Dot fill
+text = "hi"
+print(f"Dot fill    :.<8 : '{text:.<8}'")
+
+# Dash fill centered
+item = "OK"
+print(f"Dash center :-^10: '{item:-^10}'")
+
+# Underscore
+code = 7
+print(f"Underscore  :_>5 : '{code:_>5}'")
+
+
+# ============================================================================
+# Zero Padding
+# ============================================================================
+
+print("\n=== Zero Padding ===")
+
+# Basic zero padding
+n = 42
+print(f"Zero pad :05 : '{n:05}'")
+
+# Larger width
+m = 7
+print(f"Zero pad :08 : '{m:08}'")
+
+# Time-like formatting
+hours = 9
+minutes = 5
+seconds = 3
+print(f"Time: {hours:02}:{minutes:02}:{seconds:02}")
+
+
+# ============================================================================
+# Combined Format Specifiers
+# ============================================================================
+
+print("\n=== Combined Formats ===")
+
+# Width with precision
+pi = 3.14159
+print(f"Pi :10.2f  : '{pi:10.2f}'")
+
+# Right align with precision
+value = 123.456
+print(f"Value :>12.3f: '{value:>12.3f}'")
+
+
+# ============================================================================
+# Practical Examples
+# ============================================================================
+
+print("\n=== Practical Examples ===")
+
+# Financial report
+revenue = 1234567.89
+expenses = 987654.32
+profit = revenue - expenses
+
+print("Financial Summary:")
+print(f"  Revenue:  ${revenue:>15,.2f}")
+print(f"  Expenses: ${expenses:>15,.2f}")
+print(f"  Profit:   ${profit:>15,.2f}")
+
+# Table formatting
+print("\nProduct Table:")
+print(f"{'Item':<15} {'Price':>10} {'Qty':>5}")
+print(f"{'-'*15} {'-'*10} {'-'*5}")
+print(f"{'Widget':<15} {'$19.99':>10} {'100':>5}")
+print(f"{'Gadget':<15} {'$249.00':>10} {'25':>5}")
+print(f"{'Thingamajig':<15} {'$5.50':>10} {'500':>5}")
+
+# ID formatting
+print("\nID Numbers:")
+for id_num in [1, 42, 999, 10000]:
+    print(f"  ID-{id_num:06}")
diff --git a/programs/micropython/class_super.js b/programs/micropython/class_super.js
new file mode 100644
index 0000000..038d672
--- /dev/null
+++ b/programs/micropython/class_super.js
@@ -0,0 +1,520 @@
+var _pyfunc_BaseException = (function() {
+  // nargs: 0+
+  function BaseException(...args) {
+    if (!(this instanceof BaseException)) {
+      return new BaseException(...args);
+    }
+    let message = args.length > 0 ? String(args[0]) : "";
+    Error.call(this, message);
+    this.name = "BaseException";
+    this.message = message;
+    // args is always a tuple (array without _is_list) containing all constructor arguments
+    this.args = args;
+    if (Error.captureStackTrace) {
+      Error.captureStackTrace(this, BaseException);
+    }
+  }
+  BaseException.prototype = Object.create(Error.prototype);
+  BaseException.prototype.constructor = BaseException;
+  return BaseException;
+})();
+var _pyfunc_Exception = (function() {
+  // nargs: 0+
+  function Exception(...args) {
+    if (!(this instanceof Exception)) {
+      return new Exception(...args);
+    }
+    _pyfunc_BaseException.call(this, ...args);
+    this.name = "Exception";
+  }
+  Exception.prototype = Object.create(_pyfunc_BaseException.prototype);
+  Exception.prototype.constructor = Exception;
+  return Exception;
+})();
+var _pyfunc_AttributeError = (function() {
+  // nargs: 0 1
+  function AttributeError(message) {
+    if (!(this instanceof AttributeError)) {
+      return new AttributeError(message);
+    }
+    _pyfunc_Exception.call(this, message);
+    this.name = "AttributeError";
+  }
+  AttributeError.prototype = Object.create(_pyfunc_Exception.prototype);
+  AttributeError.prototype.constructor = AttributeError;
+  return AttributeError;
+})();
+var _pyfunc_TypeError_py = (function() {
+  // nargs: 0 1
+  function TypeError_py(message) {
+    if (!(this instanceof TypeError_py)) {
+      return new TypeError_py(message);
+    }
+    _pyfunc_Exception.call(this, message);
+    this.name = "TypeError";
+  }
+  TypeError_py.prototype = Object.create(_pyfunc_Exception.prototype);
+  TypeError_py.prototype.constructor = TypeError_py;
+  return TypeError_py;
+})();
+var _pyfunc_bytes_repr = function (bytes) {
+  // nargs: 1
+  // Return Python-style repr for bytes: b'...'
+  let result = "b'";
+  for (let i = 0; i < bytes.length; i++) {
+    let b = bytes[i];
+    if (b === 92) {  // backslash
+      result += "\\\\";
+    } else if (b === 39) {  // single quote
+      result += "\\'";
+    } else if (b === 10) {  // newline
+      result += "\\n";
+    } else if (b === 13) {  // carriage return
+      result += "\\r";
+    } else if (b === 9) {  // tab
+      result += "\\t";
+    } else if (b >= 32 && b < 127) {
+      // Printable ASCII
+      result += String.fromCharCode(b);
+    } else {
+      // Non-printable: use \xNN format
+      result += "\\x" + b.toString(16).padStart(2, "0");
+    }
+  }
+  result += "'";
+  return result;
+};
+var _pyfunc_hasattr = function (obj, name) {
+  // nargs: 2
+  // Check if object has attribute
+  if (obj == null) {
+    return false;
+  }
+  // Check for __getattr__
+  if (typeof obj.__getattr__ === "function") {
+    try {
+      obj.__getattr__(name);
+      return true;
+    } catch (e) {
+      return false;
+    }
+  }
+  return name in obj || obj[name] !== undefined;
+};
+var _pyfunc_op_equals = function op_equals(a, b) {
+  // nargs: 2
+  let a_type = typeof a;
+  // If a (or b actually) is of type string, number or boolean, we don't need
+  // to do all the other type checking below.
+  if (a_type === "string" || a_type === "boolean" || a_type === "number") {
+    return a == b;
+  }
+
+  if (a == null || b == null) {
+    return a == b;
+  }
+
+  // Check for __eq__ method on either object
+  if (typeof a.__eq__ === 'function') {
+    return a.__eq__(b);
+  }
+  if (typeof b.__eq__ === 'function') {
+    return b.__eq__(a);
+  }
+
+  if (Array.isArray(a) && Array.isArray(b)) {
+    let i = 0,
+      iseq = a.length == b.length;
+    while (iseq && i < a.length) {
+      iseq = op_equals(a[i], b[i]);
+      i += 1;
+    }
+    return iseq;
+  }
+
+  if (a.constructor === Object && b.constructor === Object) {
+    const akeys = Object.keys(a),
+      bkeys = Object.keys(b);
+    akeys.sort();
+    bkeys.sort();
+    let i = 0,
+      iseq = op_equals(akeys, bkeys);
+    while (iseq && i < akeys.length) {
+      const k = akeys[i];
+      iseq = op_equals(a[k], b[k]);
+      i += 1;
+    }
+    return iseq;
+  }
+
+  return a == b;
+};
+var _pyfunc_op_error = function (etype, ...args) {
+  // nargs: 1+
+  let msg = args.join(", ");
+  let e = new Error(etype + ": " + msg);
+  e.name = etype;
+  e.args = args;  // Store args for repr()
+  return e;
+};
+var _pyfunc_op_instantiate = function (ob, args) {
+  // nargs: 2
+  if (
+    typeof ob === "undefined" ||
+    (typeof window !== "undefined" && window === ob) ||
+    (typeof global !== "undefined" && global === ob)
+  ) {
+    throw "Class constructor is called as a function.";
+  }
+  for (let name in ob) {
+    if (
+      Object[name] === undefined &&
+      typeof ob[name] === "function" &&
+      !ob[name].nobind
+    ) {
+      ob[name] = ob[name].bind(ob);
+      ob[name].__name__ = name;
+    }
+  }
+  if (ob.__init__) {
+    ob.__init__.apply(ob, args);
+  }
+};
+var _pyfunc_super_proxy = function (self, classProto) {
+  // nargs: 2
+  // Creates a proxy object for super() that accesses parent class methods/attributes
+  // and binds methods to the current instance.
+  // classProto is the prototype of the class where super() is called from (not the instance's class)
+  // This is needed for multi-level inheritance to work correctly.
+  var base = classProto ? classProto._base_class : self._base_class;
+  if (!base) {
+    throw new TypeError("super(): no base class");
+  }
+  return new Proxy({}, {
+    get: function(target, prop) {
+      if (prop in base) {
+        var val = base[prop];
+        if (typeof val === 'function') {
+          return val.bind(self);
+        }
+        return val;
+      }
+      return undefined;
+    }
+  });
+};
+var _pyfunc_repr = function (x) {
+  // nargs: 1
+  // Handle null/undefined (None in Python) first
+  if (x === null || x === undefined) {
+    return "None";
+  }
+  // Handle booleans with Python-style capitalization
+  if (typeof x === "boolean") {
+    return x ? "True" : "False";
+  }
+  // Check for __repr__ method on objects (custom classes)
+  if (typeof x === "object" && x !== null && typeof x.__repr__ === "function") {
+    return x.__repr__();
+  }
+  // Handle Error objects (Python exceptions)
+  if (x instanceof Error && x.name && x.args !== undefined) {
+    let argsRepr = x.args.map(a => _pyfunc_repr(a)).join(", ");
+    return x.name + "(" + argsRepr + ")";
+  }
+  // Handle bytes (Uint8Array)
+  if (x instanceof Uint8Array) {
+    return _pyfunc_bytes_repr(x);
+  }
+  // Handle strings - use quotes like Python
+  if (typeof x === "string") {
+    // Python uses single quotes by default, but uses double quotes
+    // if the string contains single quotes but no double quotes
+    const hasSingle = x.indexOf("'") >= 0;
+    const hasDouble = x.indexOf('"') >= 0;
+    if (hasSingle && !hasDouble) {
+      // Use double quotes to avoid escaping
+      return '"' + x.replace(/\\/g, "\\\\") + '"';
+    }
+    // Default: use single quotes with escaping
+    return "'" + x.replace(/\\/g, "\\\\").replace(/'/g, "\\'") + "'";
+  }
+  // Handle arrays (lists/tuples)
+  if (Array.isArray(x)) {
+    let items = x.map(e => _pyfunc_repr(e));
+    // Arrays marked with _is_list are lists (use [])
+    // Unmarked arrays are tuples (use ())
+    if (x._is_list) {
+      return "[" + items.join(", ") + "]";
+    } else {
+      // Tuple representation - need trailing comma for single-element tuples
+      if (items.length === 1) {
+        return "(" + items[0] + ",)";
+      }
+      return "(" + items.join(", ") + ")";
+    }
+  }
+  // Handle dicts (plain objects)
+  if (typeof x === "object" && x !== null && x.constructor === Object) {
+    let entries = Object.entries(x);
+    if (entries.length === 0) {
+      return "{}";
+    }
+    let parts = entries.map(function([k, v]) {
+      let kRepr = _pyfunc_repr(k);
+      let vRepr = _pyfunc_repr(v);
+      return kRepr + ": " + vRepr;
+    });
+    return "{" + parts.join(", ") + "}";
+  }
+  // Handle numbers
+  if (typeof x === "number") {
+    return String(x);
+  }
+  let res;
+  try {
+    res = JSON.stringify(x);
+  } catch (e) {
+    res = undefined;
+  }
+  if (typeof res === "undefined") {
+    res = x._IS_COMPONENT ? x.id : String(x);
+  }
+  return res;
+};
+var _pyfunc_str = function (x) {
+  // nargs: 0 1;
+  // str() with no args returns empty string, str(None) returns "None"
+  if (arguments.length === 0) {
+    return "";
+  }
+  if (x === null || x === undefined) {
+    return "None";
+  }
+  // Handle booleans with Python-style capitalization
+  if (typeof x === "boolean") {
+    return x ? "True" : "False";
+  }
+  // Check for __str__ method on objects (custom classes)
+  if (typeof x === "object" && x !== null && typeof x.__str__ === "function") {
+    return x.__str__();
+  }
+  // Handle bytes (Uint8Array) - output like b'...'
+  if (x instanceof Uint8Array) {
+    return _pyfunc_bytes_repr(x);
+  }
+  // Handle floats - preserve .0 for whole numbers
+  if (typeof x === "number") {
+    if (Number.isFinite(x) && !Number.isInteger(x)) {
+      return String(x);
+    }
+    // Check if it was created as a float (has decimal point in source)
+    // For runtime, we check if it's a whole number that should display with .0
+    if (Number.isInteger(x)) {
+      return String(x);
+    }
+    return String(x);
+  }
+  if (Array.isArray(x)) {
+    if (x.length == 0) {
+      return "[]";
+    }
+    // Quote first element if it's a string (same as other elements)
+    let first = x[0];
+    let firstStr;
+    if (typeof first === "string") {
+      if (first.indexOf("'") == -1) {
+        firstStr = "'" + first + "'";
+      } else {
+        firstStr = JSON.stringify(first);
+      }
+    } else {
+      firstStr = _pyfunc_str(first);
+    }
+    let result = "[" + firstStr;
+    for (let i = 1; i < x.length; i++) {
+      const e = x[i];
+      if (typeof e === "string") {
+        if (e.indexOf("'") == -1) {
+          result = result.concat(", " + "'" + e + "'");
+        } else {
+          result = result.concat(", " + JSON.stringify(e));
+        }
+      } else {
+        const t = _pyfunc_str(e);
+        result = result.concat(", " + t);
+      }
+    }
+    return result + "]";
+  }
+  if (typeof x === "string") {
+    return x;
+  }
+  // Handle dicts (plain objects)
+  if (typeof x === "object" && x !== null && !Array.isArray(x) && x.constructor === Object) {
+    let entries = Object.entries(x);
+    if (entries.length === 0) {
+      return "{}";
+    }
+    let parts = entries.map(function([k, v]) {
+      let kStr = typeof k === "string" ? "'" + k + "'" : String(k);
+      let vStr = _pyfunc_repr(v);
+      return kStr + ": " + vStr;
+    });
+    return "{" + parts.join(", ") + "}";
+  }
+  // Default - use String() for objects without __str__
+  return String(x);
+};
+var _pymeth_count = function (x, start, stop) {
+  // nargs: 1 2 3
+  start = start === undefined ? 0 : start;
+  stop = stop === undefined ? this.length : stop;
+  start = Math.max(0, start < 0 ? this.length + start : start);
+  stop = Math.min(this.length, stop < 0 ? this.length + stop : stop);
+  if (Array.isArray(this)) {
+    let count = 0;
+    for (let i = 0; i < this.length; i++) {
+      if (_pyfunc_op_equals(this[i], x)) {
+        count += 1;
+      }
+    }
+    return count;
+  } else if (this.constructor == String) {
+    let count = 0,
+      i = start;
+    while (i >= 0 && i < stop) {
+      i = this.indexOf(x, i);
+      if (i < 0) break;
+      count += 1;
+      i += Math.max(1, x.length);
+    }
+    return count;
+  } else return this.count.apply(this, arguments);
+};
+Base = function () {
+    if (!(this instanceof Base)) {
+        return new Base(...arguments);
+    }
+    _pyfunc_op_instantiate(this, arguments);
+}
+Base.prototype._base_class = Object;
+Base.prototype.__name__ = "Base";
+
+Base.prototype.__init__ = function () {
+this.a = 1;
+};
+
+                Base.prototype.meth = function () {
+                console.log('in Base meth' + " " + _pyfunc_str(this.a));
+
+return null;
+                };
+
+
+Sub = function () {
+    if (!(this instanceof Sub)) {
+        return new Sub(...arguments);
+    }
+    _pyfunc_op_instantiate(this, arguments);
+}
+Sub.prototype = Object.create(Base.prototype);
+Sub.prototype._base_class = Base.prototype;
+Sub.prototype.__name__ = "Sub";
+
+                Sub.prototype.meth = function () {
+                console.log('in Sub meth');
+
+return _pyfunc_super_proxy(this, Sub.prototype).meth();
+
+                };
+
+
+const a = Sub();
+a.meth();
+
+A = function () {
+    if (!(this instanceof A)) {
+        return new A(...arguments);
+    }
+    _pyfunc_op_instantiate(this, arguments);
+}
+A.prototype._base_class = Object;
+A.prototype.__name__ = "A";
+
+                A.prototype.p = function () {
+                console.log(_pyfunc_str((_pyfunc_str(_pyfunc_super_proxy(this, A.prototype)).slice(0, 18))));
+
+return null;
+                };
+
+
+A().p();
+
+A = function () {
+    if (!(this instanceof A)) {
+        return new A(...arguments);
+    }
+    _pyfunc_op_instantiate(this, arguments);
+}
+A.prototype._base_class = Object;
+A.prototype.__name__ = "A";
+A.bar = A.prototype.bar = 123;
+                A.prototype.foo = function () {
+                console.log('A foo');
+
+return Object.assign([1, 2, 3], {_is_list: true});
+
+                };
+
+
+B = function () {
+    if (!(this instanceof B)) {
+        return new B(...arguments);
+    }
+    _pyfunc_op_instantiate(this, arguments);
+}
+B.prototype = Object.create(A.prototype);
+B.prototype._base_class = A.prototype;
+B.prototype.__name__ = "B";
+
+                B.prototype.foo = function () {
+                console.log('B foo');
+
+console.log(_pyfunc_str((_pyfunc_super_proxy(this, B.prototype).bar)));
+
+return _pymeth_count.call((_pyfunc_super_proxy(this, B.prototype).foo()), 2);
+
+                };
+
+
+console.log(_pyfunc_str((B().foo())));
+
+
+try {_pyfunc_super_proxy(1, (1).prototype);
+
+} catch(err_1) {
+    if (err_1 instanceof Error && (err_1.name === "TypeError" || err_1 instanceof _pyfunc_TypeError_py)) {console.log('TypeError');
+
+    } else { throw err_1; }
+}
+
+if ((_pyfunc_hasattr((_pyfunc_super_proxy(B(), (B).prototype)), 'foo'))) {
+} else {
+    throw _pyfunc_op_error('AssertionError');
+}
+
+try {(_pyfunc_super_proxy(B(), (B).prototype)).foo = 1;
+} catch(err_1) {
+    if (err_1 instanceof Error && (err_1.name === "AttributeError" || err_1 instanceof _pyfunc_AttributeError)) {console.log('AttributeError');
+
+    } else { throw err_1; }
+}
+
+try {
+    delete (_pyfunc_super_proxy(B(), (B).prototype)).foo;
+} catch(err_1) {
+    if (err_1 instanceof Error && (err_1.name === "AttributeError" || err_1 instanceof _pyfunc_AttributeError)) {console.log('AttributeError');
+
+    } else { throw err_1; }
+}
diff --git a/src/prescrypt/codegen/_expressions/ops.py b/src/prescrypt/codegen/_expressions/ops.py
index 35a39f4..c09ae6d 100644
--- a/src/prescrypt/codegen/_expressions/ops.py
+++ b/src/prescrypt/codegen/_expressions/ops.py
@@ -258,6 +258,21 @@ def gen_compare(node: ast.Compare, codegen: CodeGen) -> str | list:
             code = "!" + code
         return code
 
+    elif type(op) in (ast.Lt, ast.Gt, ast.LtE, ast.GtE):
+        # Optimize when both types are primitives: use native operators
+        if is_primitive(left_type) and is_primitive(right_type):
+            js_op = COMP_OP[op]
+            return f"{js_left} {js_op} {js_right}"
+        else:
+            # Unknown or non-primitive types: use helper for __lt__/__gt__/__le__/__ge__
+            op_map = {
+                ast.Lt: "op_lt",
+                ast.Gt: "op_gt",
+                ast.LtE: "op_le",
+                ast.GtE: "op_ge",
+            }
+            return codegen.call_std_function(op_map[type(op)], [js_left, js_right])
+
     else:
         js_op = COMP_OP[op]
         return f"{js_left} {js_op} {js_right}"
diff --git a/src/prescrypt/codegen/_expressions/variables.py b/src/prescrypt/codegen/_expressions/variables.py
index e4d7f0e..46eea5c 100644
--- a/src/prescrypt/codegen/_expressions/variables.py
+++ b/src/prescrypt/codegen/_expressions/variables.py
@@ -56,6 +56,7 @@
     "delattr": "delattr",
     "dir": "dir",
     "callable": "callable",
+    "property": "property",
 }
 
 
diff --git a/src/prescrypt/codegen/_statements/assignments.py b/src/prescrypt/codegen/_statements/assignments.py
index a60ef42..e9e7647 100644
--- a/src/prescrypt/codegen/_statements/assignments.py
+++ b/src/prescrypt/codegen/_statements/assignments.py
@@ -103,48 +103,55 @@ def gen_assign(node: ast.Assign, codegen: CodeGen):
 def gen_multi_target_assign(
     targets: list[ast.expr], js_value: str, codegen: CodeGen
 ) -> str:
-    """Handle multiple assignment: a = b = c = 3"""
+    """Handle multiple assignment: a = b = c = 3
+
+    Supports simple names, subscripts (a[0]), and attributes (a.x).
+    """
     lines = []
 
-    # Process targets right-to-left
-    # a = b = c = 3 -> let c = 3; let b = c; let a = b;
-    prev_name = None
-    for target in reversed(targets):
-        if not isinstance(target, ast.Name):
-            msg = "Multiple assignment only supports simple names"
-            raise JSError(msg)
+    # For non-simple targets, use a temp variable to avoid evaluating the RHS multiple times
+    needs_temp = any(not isinstance(t, ast.Name) for t in targets)
 
-        name = target.id
+    if needs_temp:
+        tmp = codegen.dummy("val")
+        lines.append(f"let {tmp} = {js_value};")
+        js_value = tmp
 
-        # Check if already known BEFORE adding
-        is_known = codegen.ns.is_known(name)
-        codegen.add_var(name)
+    # Process targets right-to-left
+    for target in reversed(targets):
+        match target:
+            case ast.Name(id=name):
+                # Check if already known BEFORE adding
+                is_known = codegen.ns.is_known(name)
+                codegen.add_var(name)
 
-        export_prefix = "export " if codegen.should_export(name) else ""
+                export_prefix = "export " if codegen.should_export(name) else ""
 
-        if is_known:
-            # Already declared - just reassign
-            if prev_name is None:
-                lines.append(f"{name} = {js_value};")
-            else:
-                lines.append(f"{name} = {prev_name};")
-        else:
-            # New variable - declare it
-            decl = codegen.get_declaration_kind(name)
-            if prev_name is None:
-                # First (rightmost) target gets the value
-                if decl:
-                    lines.append(f"{export_prefix}{decl} {name} = {js_value};")
-                else:
+                if is_known:
+                    # Already declared - just reassign
                     lines.append(f"{name} = {js_value};")
-            else:
-                # Subsequent targets get the previous variable
-                if decl:
-                    lines.append(f"{export_prefix}{decl} {name} = {prev_name};")
                 else:
-                    lines.append(f"{name} = {prev_name};")
+                    # New variable - declare it
+                    decl = codegen.get_declaration_kind(name)
+                    if decl:
+                        lines.append(f"{export_prefix}{decl} {name} = {js_value};")
+                    else:
+                        lines.append(f"{name} = {js_value};")
+
+            case ast.Subscript(value, slice_node):
+                js_obj = flatten(codegen.gen_expr(value))
+                js_key = flatten(codegen.gen_expr(slice_node))
+                lines.append(
+                    f"{codegen.call_std_function('op_setitem', [js_obj, js_key, js_value])};"
+                )
 
-        prev_name = name
+            case ast.Attribute(value, attr):
+                js_obj = flatten(codegen.gen_expr(value))
+                lines.append(f"{js_obj}.{attr} = {js_value};")
+
+            case _:
+                msg = f"Multiple assignment does not support {type(target).__name__}"
+                raise JSError(msg)
 
     return "\n".join(lines)
 
@@ -455,17 +462,26 @@ def gen_delete(node: ast.Delete, codegen: CodeGen) -> str:
                     )
             else:
                 # del obj[key] or del lst[idx]
-                # Use splice for arrays, delete for objects
-                # At runtime, check if it's an array and use appropriate method
+                # Use op_delitem for __delitem__ support
                 js_key = flatten(codegen.gen_expr(slice_node))
                 code.append(
                     codegen.lf(
-                        f"if (Array.isArray({js_value})) {{ {js_value}.splice({js_key}, 1); }} "
-                        f"else {{ delete {js_value}[{js_key}]; }}"
+                        codegen.call_std_function("op_delitem", [js_value, js_key])
+                        + ";"
                     )
                 )
+        elif isinstance(target, ast.Attribute):
+            # del obj.attr - use runtime helper to check for property deleters
+            js_obj = flatten(codegen.gen_expr(target.value))
+            attr_name = target.attr
+            code.append(
+                codegen.lf(
+                    codegen.call_std_function("op_delattr", [js_obj, f'"{attr_name}"'])
+                    + ";"
+                )
+            )
         else:
-            # del var or del obj.attr - use JS delete
+            # del var - use JS delete
             code.append(codegen.lf("delete "))
             code += codegen.gen_expr(target)
             code.append(";")
diff --git a/src/prescrypt/codegen/_statements/classes.py b/src/prescrypt/codegen/_statements/classes.py
index 2aa6125..e30b89b 100644
--- a/src/prescrypt/codegen/_statements/classes.py
+++ b/src/prescrypt/codegen/_statements/classes.py
@@ -128,7 +128,12 @@ def _collect_properties(body_nodes: list) -> dict:
 def _make_property_definition(
     class_name: str, prop_name: str, prop_info: dict, codegen
 ) -> str:
-    """Generate Object.defineProperty() call for a property."""
+    """Generate Object.defineProperty() call for a property.
+
+    Note: JavaScript property descriptors don't support a 'delete' handler.
+    We store deleters as __deleter_propname__ methods on the prototype and
+    the runtime op_delattr checks for them.
+    """
     parts = []
     parts.append(
         f"Object.defineProperty({class_name}.prototype, {js_repr(prop_name)}, {{"
@@ -147,15 +152,25 @@ def _make_property_definition(
             value_param = "value"
         setter_body = _gen_property_function_body(setter_node, codegen)
         parts.append(f"    set: function({value_param}) {{ {setter_body} }},")
-
-    if "deleter" in prop_info:
-        deleter_body = _gen_property_function_body(prop_info["deleter"], codegen)
-        parts.append(f"    delete: function() {{ {deleter_body} }},")
+    elif "getter" in prop_info:
+        # Read-only property: add a setter that throws AttributeError
+        parts.append(
+            f"    set: function(v) {{ throw _pyfunc_op_error('AttributeError', "
+            f"\"property '{prop_name}' has no setter\"); }},"
+        )
 
     parts.append("    configurable: true")
     parts.append("});")
 
-    return "\n".join(parts)
+    result = "\n".join(parts)
+
+    # Handle deleter separately - store as __deleter_propname__ method
+    if "deleter" in prop_info:
+        deleter_body = _gen_property_function_body(prop_info["deleter"], codegen)
+        deleter_name = f"__deleter_{prop_name}__"
+        result += f"\n{class_name}.prototype.{deleter_name} = function() {{ {deleter_body} }};"
+
+    return result
 
 
 def _gen_property_function_body(node: ast.FunctionDef, codegen) -> str:
@@ -192,7 +207,8 @@ def make_class_definition(
     """
     # Create constructor that works with or without 'new' keyword
     # ES6 export requires 'const' keyword: export const X = ...
-    decl = "export const " if export else ""
+    # Non-exported classes need 'var' to avoid strict mode errors
+    decl = "export const " if export else "var "
     lines = [f"{decl}{name} = function () {{"]
     # Auto-instantiate if called without 'new'
     lines.append(f"    if (!(this instanceof {name})) {{")
diff --git a/src/prescrypt/codegen/_statements/functions.py b/src/prescrypt/codegen/_statements/functions.py
index 7149634..0f69191 100644
--- a/src/prescrypt/codegen/_statements/functions.py
+++ b/src/prescrypt/codegen/_statements/functions.py
@@ -268,13 +268,18 @@ def _gen_args_no_self_conversion(self) -> str:
         return "".join(code)
 
     def _gen_args_cls_to_name(self, class_name: str) -> str:
-        """Generate args, skipping cls parameter (for classmethod)."""
+        """Generate args, skipping first parameter (for classmethod).
+
+        Python's @classmethod convention uses 'cls' as first param, but
+        some code (like MicroPython tests) uses 'self'. We skip the first
+        param regardless of name since it represents the class.
+        """
         args = self.node.args.args
         code = []
         for i, arg in enumerate(args):
             name = arg.arg
-            if i == 0 and name == "cls":
-                # Skip cls - we'll inject it as a local variable
+            if i == 0:
+                # Skip first param (cls/self) - we'll inject cls as a local variable
                 continue
             code.append(name)
             code.append(", ")
diff --git a/src/prescrypt/stdlibjs/_stdlib.js b/src/prescrypt/stdlibjs/_stdlib.js
index b1e06cc..4e2d53b 100644
--- a/src/prescrypt/stdlibjs/_stdlib.js
+++ b/src/prescrypt/stdlibjs/_stdlib.js
@@ -430,6 +430,22 @@ var _pyfunc_op_add = function (a, b) {
   }
   return a + b;
 };
+var _pyfunc_op_delitem = function op_delitem(obj, key) {
+  // nargs: 2
+  // Python del obj[key] - checks for __delitem__ method first
+  if (obj == null) {
+    throw new TypeError("'NoneType' object does not support item deletion");
+  }
+  if (typeof obj.__delitem__ === 'function') {
+    obj.__delitem__(key);
+  } else if (Array.isArray(obj)) {
+    // For arrays, use splice to remove element
+    obj.splice(key, 1);
+  } else {
+    // For objects, use delete
+    delete obj[key];
+  }
+};
 var _pyfunc_op_equals = function op_equals(a, b) {
   // nargs: 2
   let a_type = typeof a;
@@ -716,6 +732,40 @@ var _pyfunc_oct = function (x) {
   }
   return "0o" + x.toString(8);
 };
+var _pyfunc_op_delattr = function op_delattr(obj, name) {
+  // nargs: 2
+  // Python del obj.attr - checks for property deleters first
+  if (obj == null) {
+    throw _pyfunc_op_error('AttributeError', "'NoneType' object has no attribute '" + name + "'");
+  }
+  // Check for property deleter (__deleter_propname__ method on prototype)
+  var deleterName = '__deleter_' + name + '__';
+  var proto = Object.getPrototypeOf(obj);
+  if (proto && typeof proto[deleterName] === 'function') {
+    proto[deleterName].call(obj);
+    return;
+  }
+  // Check for __delattr__ method
+  if (typeof obj.__delattr__ === 'function') {
+    obj.__delattr__(name);
+    return;
+  }
+  // Fall back to regular delete
+  if (name in obj) {
+    delete obj[name];
+  } else {
+    var typeName = obj.constructor ? obj.constructor.name : typeof obj;
+    throw _pyfunc_op_error('AttributeError', "'" + typeName + "' object has no attribute '" + name + "'");
+  }
+};
+var _pyfunc_op_ge = function op_ge(a, b) {
+  // nargs: 2
+  // Check for __ge__ method on the left operand
+  if (a != null && typeof a.__ge__ === 'function') {
+    return a.__ge__(b);
+  }
+  return a >= b;
+};
 var _pyfunc_op_getitem = function op_getitem(obj, key) {
   // nargs: 2
   // Python obj[key] - checks for __getitem__ method first
@@ -731,6 +781,14 @@ var _pyfunc_op_getitem = function op_getitem(obj, key) {
   }
   return obj[key];
 };
+var _pyfunc_op_gt = function op_gt(a, b) {
+  // nargs: 2
+  // Check for __gt__ method on the left operand
+  if (a != null && typeof a.__gt__ === 'function') {
+    return a.__gt__(b);
+  }
+  return a > b;
+};
 var _pyfunc_op_instantiate = function (ob, args) {
   // nargs: 2
   if (
@@ -754,6 +812,14 @@ var _pyfunc_op_instantiate = function (ob, args) {
     ob.__init__.apply(ob, args);
   }
 };
+var _pyfunc_op_le = function op_le(a, b) {
+  // nargs: 2
+  // Check for __le__ method on the left operand
+  if (a != null && typeof a.__le__ === 'function') {
+    return a.__le__(b);
+  }
+  return a <= b;
+};
 var _pyfunc_op_len = function op_len(obj) {
   // nargs: 1
   // Python len() - checks for __len__ method first, then falls back to .length
@@ -775,6 +841,14 @@ var _pyfunc_op_len = function op_len(obj) {
   }
   throw new TypeError("object has no len()");
 };
+var _pyfunc_op_lt = function op_lt(a, b) {
+  // nargs: 2
+  // Check for __lt__ method on the left operand
+  if (a != null && typeof a.__lt__ === 'function') {
+    return a.__lt__(b);
+  }
+  return a < b;
+};
 var _pyfunc_op_matmul = function (a, b) {
   // nargs: 2
   // Matrix multiplication operator @
@@ -1044,8 +1118,22 @@ var _pyfunc_super_proxy = function (self, classProto) {
   if (!base) {
     throw new TypeError("super(): no base class");
   }
+  var className = classProto ? classProto.__name__ : (self.__name__ || 'object');
   return new Proxy({}, {
     get: function(target, prop) {
+      // Handle string conversion
+      if (prop === '__str__' || prop === 'toString') {
+        return function() {
+          return '<super: <class \'' + className + '\'>, <' + className + ' object>>';
+        };
+      }
+      if (prop === Symbol.toStringTag) {
+        return 'super';
+      }
+      // Handle hasattr-style checks
+      if (prop === '__class__') {
+        return 'super';
+      }
       if (prop in base) {
         var val = base[prop];
         if (typeof val === 'function') {
@@ -1053,7 +1141,25 @@ var _pyfunc_super_proxy = function (self, classProto) {
         }
         return val;
       }
+      // Special case: __init__ on Object base class is a no-op
+      // This allows super().__init__() to work when inheriting from object
+      if (prop === '__init__' && (base === Object || base === Object.prototype)) {
+        return function() {};
+      }
       return undefined;
+    },
+    set: function(target, prop, value) {
+      throw _pyfunc_op_error('AttributeError', "'super' object attribute '" + prop + "' is read-only");
+    },
+    deleteProperty: function(target, prop) {
+      throw _pyfunc_op_error('AttributeError', "'super' object attribute '" + prop + "' is read-only");
+    },
+    has: function(target, prop) {
+      // Support 'in' operator and hasattr()
+      if (prop === '__str__' || prop === 'toString' || prop === '__class__') {
+        return true;
+      }
+      return prop in base;
     }
   });
 };
@@ -1158,8 +1264,9 @@ var _pyfunc_format = function (v, fmt) {
   if (fmt === undefined) {
     return String(v);
   }
-  fmt = fmt.toLowerCase();
   let s = String(v);
+
+  // Handle !r conversion (repr)
   if (fmt.indexOf("!r") >= 0) {
     try {
       s = JSON.stringify(v);
@@ -1169,65 +1276,103 @@ var _pyfunc_format = function (v, fmt) {
     if (typeof s === "undefined") {
       s = v._IS_COMPONENT ? v.id : String(v);
     }
+    fmt = fmt.replace("!r", "");
   }
-  let fmt_type = "";
-  if (
-    fmt.slice(-1) == "i" ||
-    fmt.slice(-1) == "f" ||
-    fmt.slice(-1) == "e" ||
-    fmt.slice(-1) == "g"
-  ) {
-    fmt_type = fmt[fmt.length - 1];
-    fmt = fmt.slice(0, fmt.length - 1);
-  }
+
+  // Parse format spec: [[fill]align][sign][#][0][width][,][.precision][type]
+  // The format can be either ":spec" (from f-strings) or just "spec" (from format() builtin)
   let i0 = fmt.indexOf(":");
-  let i1 = fmt.indexOf(".");
-  let spec1 = "",
-    spec2 = ""; // before and after dot
-  if (i0 >= 0) {
-    if (i1 > i0) {
-      spec1 = fmt.slice(i0 + 1, i1);
-      spec2 = fmt.slice(i1 + 1);
-    } else {
-      spec1 = fmt.slice(i0 + 1);
+  let spec = i0 >= 0 ? fmt.slice(i0 + 1) : fmt;
+
+  // Parse fill and alignment
+  let fill = ' ';
+  let align = '';
+  if (spec.length >= 2 && ['<', '>', '^', '='].includes(spec[1])) {
+    fill = spec[0];
+    align = spec[1];
+    spec = spec.slice(2);
+  } else if (spec.length >= 1 && ['<', '>', '^', '='].includes(spec[0])) {
+    align = spec[0];
+    spec = spec.slice(1);
+  }
+
+  // Parse sign
+  let prefix = "";
+  if (spec.length > 0 && ['+', '-', ' '].includes(spec[0])) {
+    if (spec[0] === '+' && typeof v === 'number' && v >= 0) {
+      prefix = '+';
+    } else if (spec[0] === ' ' && typeof v === 'number' && v >= 0) {
+      prefix = ' ';
     }
-  } else if (i1 >= 0) {
-    // No colon, but has dot (e.g., ".2f" after removing "f")
-    spec1 = fmt.slice(0, i1);
-    spec2 = fmt.slice(i1 + 1);
+    spec = spec.slice(1);
   }
-  // Format numbers
-  if (fmt_type == "") {
-  } else if (fmt_type == "i") {
-    // integer formatting, for %i
+
+  // Parse # (alternate form) - skip for now
+  if (spec.length > 0 && spec[0] === '#') {
+    spec = spec.slice(1);
+  }
+
+  // Check for thousands separator
+  let useThousands = false;
+  if (spec.indexOf(',') >= 0) {
+    useThousands = true;
+    spec = spec.replace(',', '');
+  }
+
+  // Handle zero-fill shorthand: 05 means 0>5 for numbers
+  if (spec.length > 0 && spec[0] === '0' && !align) {
+    fill = '0';
+    align = '>';
+    spec = spec.slice(1);
+  }
+
+  // Parse width
+  let width = 0;
+  let widthMatch = spec.match(/^(\d+)/);
+  if (widthMatch) {
+    width = parseInt(widthMatch[1], 10);
+    spec = spec.slice(widthMatch[1].length);
+  }
+
+  // Parse precision
+  let precision = null;
+  if (spec.length > 0 && spec[0] === '.') {
+    spec = spec.slice(1);
+    let precMatch = spec.match(/^(\d+)/);
+    if (precMatch) {
+      precision = parseInt(precMatch[1], 10);
+      spec = spec.slice(precMatch[1].length);
+    }
+  }
+
+  // Parse type (remaining characters)
+  let fmt_type = spec.toLowerCase();
+
+  // Format the value based on type
+  if (fmt_type === 'd' || fmt_type === 'i') {
     s = parseInt(v).toFixed(0);
-  } else if (fmt_type == "f") {
-    // float formatting
+  } else if (fmt_type === 'f') {
     v = parseFloat(v);
-    let decimals = spec2 ? Number(spec2) : 6;
+    let decimals = precision !== null ? precision : 6;
     s = v.toFixed(decimals);
-  } else if (fmt_type == "e") {
-    // exp formatting
+  } else if (fmt_type === 'e') {
     v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    s = v.toExponential(precision);
-  } else if (fmt_type == "g") {
-    // "general" formatting
+    let prec = precision !== null ? precision : 6;
+    s = v.toExponential(prec);
+  } else if (fmt_type === 'g') {
     v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    // Exp or decimal?
-    s = v.toExponential(precision - 1);
+    let prec = (precision !== null ? precision : 6) || 1;
+    s = v.toExponential(prec - 1);
     let s1 = s.slice(0, s.indexOf("e")),
       s2 = s.slice(s.indexOf("e"));
     if (s2.length == 3) {
       s2 = "e" + s2[1] + "0" + s2[2];
     }
     let exp = Number(s2.slice(1));
-    if (exp >= -4 && exp < precision) {
-      s1 = v.toPrecision(precision);
+    if (exp >= -4 && exp < prec) {
+      s1 = v.toPrecision(prec);
       s2 = "";
     }
-    // Skip trailing zeros and dot
     let j = s1.length - 1;
     while (j > 0 && s1[j] == "0") {
       j -= 1;
@@ -1237,22 +1382,59 @@ var _pyfunc_format = function (v, fmt) {
       s1 = s1.slice(0, s1.length - 1);
     }
     s = s1 + s2;
-  }
-  // prefix/padding
-  let prefix = "";
-  if (spec1) {
-    if (spec1[0] == "+" && v > 0) {
-      prefix = "+";
-      spec1 = spec1.slice(1);
-    } else if (spec1[0] == " " && v > 0) {
-      prefix = " ";
-      spec1 = spec1.slice(1);
+  } else if (fmt_type === '' && precision !== null && typeof v === 'number') {
+    // No type but has precision - treat as float
+    s = parseFloat(v).toFixed(precision);
+  }
+
+  // Apply thousands separator
+  if (useThousands && !isNaN(parseFloat(v))) {
+    let parts = s.split('.');
+    let intPart = parts[0];
+    let sign = '';
+    if (intPart[0] === '-') {
+      sign = '-';
+      intPart = intPart.slice(1);
+    }
+    // Add commas to integer part using regex
+    intPart = intPart.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
+    parts[0] = sign + intPart;
+    s = parts.join('.');
+  }
+
+  // Apply width and alignment padding
+  if (width > 0) {
+    let totalLen = s.length + prefix.length;
+    if (totalLen < width) {
+      let padLen = width - totalLen;
+      let padding = fill.repeat(padLen);
+      if (align === '<') {
+        // Left align - padding on right
+        s = prefix + s + padding;
+        prefix = '';
+      } else if (align === '^') {
+        // Center align
+        let left = Math.floor(padLen / 2);
+        let right = padLen - left;
+        s = fill.repeat(left) + prefix + s + fill.repeat(right);
+        prefix = '';
+      } else if (align === '=' && prefix) {
+        // Sign-aware padding (padding between sign and digits)
+        s = prefix + padding + s;
+        prefix = '';
+      } else {
+        // Default: right align ('>') - padding on left
+        if (fill === '0' && prefix) {
+          // Zero padding goes after sign
+          s = prefix + padding + s;
+          prefix = '';
+        } else {
+          s = padding + s;
+        }
+      }
     }
   }
-  if (spec1 && spec1[0] == "0") {
-    let padding = Number(spec1.slice(1)) - (s.length + prefix.length);
-    s = "0".repeat(Math.max(0, padding)) + s;
-  }
+
   return prefix + s;
 };
 var _pyfunc_format_value = function (value, type, flags, width, precision) {
@@ -1477,6 +1659,27 @@ var _pyfunc_op_mod = function (left, right) {
   }
   return left % right;
 };
+var _pyfunc_property = function (fget, fset, fdel, doc) {
+  // nargs: 0 1 2 3 4
+  // Python property builtin - creates a property descriptor
+  var prop = {
+    __class__: 'property',
+    fget: fget || null,
+    fset: fset || null,
+    fdel: fdel || null,
+    __doc__: doc || null,
+    getter: function(fn) {
+      return _pyfunc_property(fn, this.fset, this.fdel, this.__doc__);
+    },
+    setter: function(fn) {
+      return _pyfunc_property(this.fget, fn, this.fdel, this.__doc__);
+    },
+    deleter: function(fn) {
+      return _pyfunc_property(this.fget, this.fset, fn, this.__doc__);
+    }
+  };
+  return prop;
+};
 var _pyfunc_repr = function (x) {
   // nargs: 1
   // Handle null/undefined (None in Python) first
diff --git a/src/prescrypt/stdlibjs/functions.js b/src/prescrypt/stdlibjs/functions.js
index 4285b13..dcc2685 100644
--- a/src/prescrypt/stdlibjs/functions.js
+++ b/src/prescrypt/stdlibjs/functions.js
@@ -341,8 +341,22 @@ export const super_proxy = function (self, classProto) {
   if (!base) {
     throw new TypeError("super(): no base class");
   }
+  var className = classProto ? classProto.__name__ : (self.__name__ || 'object');
   return new Proxy({}, {
     get: function(target, prop) {
+      // Handle string conversion
+      if (prop === '__str__' || prop === 'toString') {
+        return function() {
+          return '<super: <class \'' + className + '\'>, <' + className + ' object>>';
+        };
+      }
+      if (prop === Symbol.toStringTag) {
+        return 'super';
+      }
+      // Handle hasattr-style checks
+      if (prop === '__class__') {
+        return 'super';
+      }
       if (prop in base) {
         var val = base[prop];
         if (typeof val === 'function') {
@@ -350,7 +364,25 @@ export const super_proxy = function (self, classProto) {
         }
         return val;
       }
+      // Special case: __init__ on Object base class is a no-op
+      // This allows super().__init__() to work when inheriting from object
+      if (prop === '__init__' && (base === Object || base === Object.prototype)) {
+        return function() {};
+      }
       return undefined;
+    },
+    set: function(target, prop, value) {
+      throw FUNCTION_PREFIXop_error('AttributeError', "'super' object attribute '" + prop + "' is read-only");
+    },
+    deleteProperty: function(target, prop) {
+      throw FUNCTION_PREFIXop_error('AttributeError', "'super' object attribute '" + prop + "' is read-only");
+    },
+    has: function(target, prop) {
+      // Support 'in' operator and hasattr()
+      if (prop === '__str__' || prop === 'toString' || prop === '__class__') {
+        return true;
+      }
+      return prop in base;
     }
   });
 };
@@ -639,8 +671,9 @@ export const format = function (v, fmt) {
   if (fmt === undefined) {
     return String(v);
   }
-  fmt = fmt.toLowerCase();
   let s = String(v);
+
+  // Handle !r conversion (repr)
   if (fmt.indexOf("!r") >= 0) {
     try {
       s = JSON.stringify(v);
@@ -650,65 +683,103 @@ export const format = function (v, fmt) {
     if (typeof s === "undefined") {
       s = v._IS_COMPONENT ? v.id : String(v);
     }
+    fmt = fmt.replace("!r", "");
   }
-  let fmt_type = "";
-  if (
-    fmt.slice(-1) == "i" ||
-    fmt.slice(-1) == "f" ||
-    fmt.slice(-1) == "e" ||
-    fmt.slice(-1) == "g"
-  ) {
-    fmt_type = fmt[fmt.length - 1];
-    fmt = fmt.slice(0, fmt.length - 1);
-  }
+
+  // Parse format spec: [[fill]align][sign][#][0][width][,][.precision][type]
+  // The format can be either ":spec" (from f-strings) or just "spec" (from format() builtin)
   let i0 = fmt.indexOf(":");
-  let i1 = fmt.indexOf(".");
-  let spec1 = "",
-    spec2 = ""; // before and after dot
-  if (i0 >= 0) {
-    if (i1 > i0) {
-      spec1 = fmt.slice(i0 + 1, i1);
-      spec2 = fmt.slice(i1 + 1);
-    } else {
-      spec1 = fmt.slice(i0 + 1);
+  let spec = i0 >= 0 ? fmt.slice(i0 + 1) : fmt;
+
+  // Parse fill and alignment
+  let fill = ' ';
+  let align = '';
+  if (spec.length >= 2 && ['<', '>', '^', '='].includes(spec[1])) {
+    fill = spec[0];
+    align = spec[1];
+    spec = spec.slice(2);
+  } else if (spec.length >= 1 && ['<', '>', '^', '='].includes(spec[0])) {
+    align = spec[0];
+    spec = spec.slice(1);
+  }
+
+  // Parse sign
+  let prefix = "";
+  if (spec.length > 0 && ['+', '-', ' '].includes(spec[0])) {
+    if (spec[0] === '+' && typeof v === 'number' && v >= 0) {
+      prefix = '+';
+    } else if (spec[0] === ' ' && typeof v === 'number' && v >= 0) {
+      prefix = ' ';
+    }
+    spec = spec.slice(1);
+  }
+
+  // Parse # (alternate form) - skip for now
+  if (spec.length > 0 && spec[0] === '#') {
+    spec = spec.slice(1);
+  }
+
+  // Check for thousands separator
+  let useThousands = false;
+  if (spec.indexOf(',') >= 0) {
+    useThousands = true;
+    spec = spec.replace(',', '');
+  }
+
+  // Handle zero-fill shorthand: 05 means 0>5 for numbers
+  if (spec.length > 0 && spec[0] === '0' && !align) {
+    fill = '0';
+    align = '>';
+    spec = spec.slice(1);
+  }
+
+  // Parse width
+  let width = 0;
+  let widthMatch = spec.match(/^(\d+)/);
+  if (widthMatch) {
+    width = parseInt(widthMatch[1], 10);
+    spec = spec.slice(widthMatch[1].length);
+  }
+
+  // Parse precision
+  let precision = null;
+  if (spec.length > 0 && spec[0] === '.') {
+    spec = spec.slice(1);
+    let precMatch = spec.match(/^(\d+)/);
+    if (precMatch) {
+      precision = parseInt(precMatch[1], 10);
+      spec = spec.slice(precMatch[1].length);
     }
-  } else if (i1 >= 0) {
-    // No colon, but has dot (e.g., ".2f" after removing "f")
-    spec1 = fmt.slice(0, i1);
-    spec2 = fmt.slice(i1 + 1);
   }
-  // Format numbers
-  if (fmt_type == "") {
-  } else if (fmt_type == "i") {
-    // integer formatting, for %i
+
+  // Parse type (remaining characters)
+  let fmt_type = spec.toLowerCase();
+
+  // Format the value based on type
+  if (fmt_type === 'd' || fmt_type === 'i') {
     s = parseInt(v).toFixed(0);
-  } else if (fmt_type == "f") {
-    // float formatting
+  } else if (fmt_type === 'f') {
     v = parseFloat(v);
-    let decimals = spec2 ? Number(spec2) : 6;
+    let decimals = precision !== null ? precision : 6;
     s = v.toFixed(decimals);
-  } else if (fmt_type == "e") {
-    // exp formatting
+  } else if (fmt_type === 'e') {
     v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    s = v.toExponential(precision);
-  } else if (fmt_type == "g") {
-    // "general" formatting
+    let prec = precision !== null ? precision : 6;
+    s = v.toExponential(prec);
+  } else if (fmt_type === 'g') {
     v = parseFloat(v);
-    let precision = (spec2 ? Number(spec2) : 6) || 1;
-    // Exp or decimal?
-    s = v.toExponential(precision - 1);
+    let prec = (precision !== null ? precision : 6) || 1;
+    s = v.toExponential(prec - 1);
     let s1 = s.slice(0, s.indexOf("e")),
       s2 = s.slice(s.indexOf("e"));
     if (s2.length == 3) {
       s2 = "e" + s2[1] + "0" + s2[2];
     }
     let exp = Number(s2.slice(1));
-    if (exp >= -4 && exp < precision) {
-      s1 = v.toPrecision(precision);
+    if (exp >= -4 && exp < prec) {
+      s1 = v.toPrecision(prec);
       s2 = "";
     }
-    // Skip trailing zeros and dot
     let j = s1.length - 1;
     while (j > 0 && s1[j] == "0") {
       j -= 1;
@@ -718,22 +789,59 @@ export const format = function (v, fmt) {
       s1 = s1.slice(0, s1.length - 1);
     }
     s = s1 + s2;
-  }
-  // prefix/padding
-  let prefix = "";
-  if (spec1) {
-    if (spec1[0] == "+" && v > 0) {
-      prefix = "+";
-      spec1 = spec1.slice(1);
-    } else if (spec1[0] == " " && v > 0) {
-      prefix = " ";
-      spec1 = spec1.slice(1);
+  } else if (fmt_type === '' && precision !== null && typeof v === 'number') {
+    // No type but has precision - treat as float
+    s = parseFloat(v).toFixed(precision);
+  }
+
+  // Apply thousands separator
+  if (useThousands && !isNaN(parseFloat(v))) {
+    let parts = s.split('.');
+    let intPart = parts[0];
+    let sign = '';
+    if (intPart[0] === '-') {
+      sign = '-';
+      intPart = intPart.slice(1);
+    }
+    // Add commas to integer part using regex
+    intPart = intPart.replace(/\B(?=(\d{3})+(?!\d))/g, ',');
+    parts[0] = sign + intPart;
+    s = parts.join('.');
+  }
+
+  // Apply width and alignment padding
+  if (width > 0) {
+    let totalLen = s.length + prefix.length;
+    if (totalLen < width) {
+      let padLen = width - totalLen;
+      let padding = fill.repeat(padLen);
+      if (align === '<') {
+        // Left align - padding on right
+        s = prefix + s + padding;
+        prefix = '';
+      } else if (align === '^') {
+        // Center align
+        let left = Math.floor(padLen / 2);
+        let right = padLen - left;
+        s = fill.repeat(left) + prefix + s + fill.repeat(right);
+        prefix = '';
+      } else if (align === '=' && prefix) {
+        // Sign-aware padding (padding between sign and digits)
+        s = prefix + padding + s;
+        prefix = '';
+      } else {
+        // Default: right align ('>') - padding on left
+        if (fill === '0' && prefix) {
+          // Zero padding goes after sign
+          s = prefix + padding + s;
+          prefix = '';
+        } else {
+          s = padding + s;
+        }
+      }
     }
   }
-  if (spec1 && spec1[0] == "0") {
-    let padding = Number(spec1.slice(1)) - (s.length + prefix.length);
-    s = "0".repeat(Math.max(0, padding)) + s;
-  }
+
   return prefix + s;
 };
 
@@ -1349,6 +1457,31 @@ export const bool = function (x) {
 
 // ---
 
+// function: property
+export const property = function (fget, fset, fdel, doc) {
+  // nargs: 0 1 2 3 4
+  // Python property builtin - creates a property descriptor
+  var prop = {
+    __class__: 'property',
+    fget: fget || null,
+    fset: fset || null,
+    fdel: fdel || null,
+    __doc__: doc || null,
+    getter: function(fn) {
+      return FUNCTION_PREFIXproperty(fn, this.fset, this.fdel, this.__doc__);
+    },
+    setter: function(fn) {
+      return FUNCTION_PREFIXproperty(this.fget, fn, this.fdel, this.__doc__);
+    },
+    deleter: function(fn) {
+      return FUNCTION_PREFIXproperty(this.fget, this.fset, fn, this.__doc__);
+    }
+  };
+  return prop;
+};
+
+// ---
+
 // function: abs
 export const abs = Math.abs; // nargs: 1;
 
@@ -1746,6 +1879,56 @@ export const op_setitem = function op_setitem(obj, key, value) {
 
 // ---
 
+// function: op_delitem
+export const op_delitem = function op_delitem(obj, key) {
+  // nargs: 2
+  // Python del obj[key] - checks for __delitem__ method first
+  if (obj == null) {
+    throw new TypeError("'NoneType' object does not support item deletion");
+  }
+  if (typeof obj.__delitem__ === 'function') {
+    obj.__delitem__(key);
+  } else if (Array.isArray(obj)) {
+    // For arrays, use splice to remove element
+    obj.splice(key, 1);
+  } else {
+    // For objects, use delete
+    delete obj[key];
+  }
+};
+
+// ---
+
+// function: op_delattr
+export const op_delattr = function op_delattr(obj, name) {
+  // nargs: 2
+  // Python del obj.attr - checks for property deleters first
+  if (obj == null) {
+    throw FUNCTION_PREFIXop_error('AttributeError', "'NoneType' object has no attribute '" + name + "'");
+  }
+  // Check for property deleter (__deleter_propname__ method on prototype)
+  var deleterName = '__deleter_' + name + '__';
+  var proto = Object.getPrototypeOf(obj);
+  if (proto && typeof proto[deleterName] === 'function') {
+    proto[deleterName].call(obj);
+    return;
+  }
+  // Check for __delattr__ method
+  if (typeof obj.__delattr__ === 'function') {
+    obj.__delattr__(name);
+    return;
+  }
+  // Fall back to regular delete
+  if (name in obj) {
+    delete obj[name];
+  } else {
+    var typeName = obj.constructor ? obj.constructor.name : typeof obj;
+    throw FUNCTION_PREFIXop_error('AttributeError', "'" + typeName + "' object has no attribute '" + name + "'");
+  }
+};
+
+// ---
+
 // function: op_equals
 export const op_equals = function op_equals(a, b) {
   // nargs: 2
@@ -1798,6 +1981,54 @@ export const op_equals = function op_equals(a, b) {
 
 // ---
 
+// function: op_lt
+export const op_lt = function op_lt(a, b) {
+  // nargs: 2
+  // Check for __lt__ method on the left operand
+  if (a != null && typeof a.__lt__ === 'function') {
+    return a.__lt__(b);
+  }
+  return a < b;
+};
+
+// ---
+
+// function: op_gt
+export const op_gt = function op_gt(a, b) {
+  // nargs: 2
+  // Check for __gt__ method on the left operand
+  if (a != null && typeof a.__gt__ === 'function') {
+    return a.__gt__(b);
+  }
+  return a > b;
+};
+
+// ---
+
+// function: op_le
+export const op_le = function op_le(a, b) {
+  // nargs: 2
+  // Check for __le__ method on the left operand
+  if (a != null && typeof a.__le__ === 'function') {
+    return a.__le__(b);
+  }
+  return a <= b;
+};
+
+// ---
+
+// function: op_ge
+export const op_ge = function op_ge(a, b) {
+  // nargs: 2
+  // Check for __ge__ method on the left operand
+  if (a != null && typeof a.__ge__ === 'function') {
+    return a.__ge__(b);
+  }
+  return a >= b;
+};
+
+// ---
+
 // function: op_contains
 export const op_contains = function op_contains(a, b) {
   // nargs: 2
diff --git a/tests/a_unit/codegen/expressions/test_f_strings.py b/tests/a_unit/codegen/expressions/test_f_strings.py
index a050b26..f57643f 100644
--- a/tests/a_unit/codegen/expressions/test_f_strings.py
+++ b/tests/a_unit/codegen/expressions/test_f_strings.py
@@ -156,3 +156,67 @@ def test_multiline_fstring(self):
         result = js_eval(py2js(code))
         assert "x = 1" in result
         assert "y = 2" in result
+
+
+class TestFStringThousandsSeparator:
+    """Test f-string thousands separator (:,) format specifier."""
+
+    def test_thousands_integer(self):
+        """Thousands separator on integer."""
+        assert js_eval(py2js("x = 1234567; f'{x:,}'")) == "1,234,567"
+
+    def test_thousands_negative(self):
+        """Thousands separator on negative integer."""
+        assert js_eval(py2js("x = -1234567; f'{x:,}'")) == "-1,234,567"
+
+    def test_thousands_with_precision(self):
+        """Thousands separator combined with float precision."""
+        assert js_eval(py2js("x = 1234567.89; f'{x:,.2f}'")) == "1,234,567.89"
+
+    def test_thousands_small(self):
+        """Thousands separator on small number (no commas needed)."""
+        assert js_eval(py2js("x = 123; f'{x:,}'")) == "123"
+
+    def test_thousands_zero(self):
+        """Thousands separator on zero."""
+        assert js_eval(py2js("x = 0; f'{x:,}'")) == "0"
+
+
+class TestFStringAlignment:
+    """Test f-string width and alignment format specifiers."""
+
+    def test_right_align(self):
+        """Right align with > specifier."""
+        result = js_eval(py2js("x = 42; f'{x:>10}'"))
+        assert result == "        42"
+        assert len(result) == 10
+
+    def test_left_align(self):
+        """Left align with < specifier."""
+        result = js_eval(py2js("s = 'hi'; f'{s:<10}'"))
+        assert result == "hi        "
+        assert len(result) == 10
+
+    def test_center_align(self):
+        """Center align with ^ specifier."""
+        result = js_eval(py2js("x = 42; f'{x:^10}'"))
+        assert len(result) == 10
+        assert result.strip() == "42"
+
+    def test_custom_fill(self):
+        """Custom fill character with alignment."""
+        assert js_eval(py2js("x = 42; f'{x:*>5}'")) == "***42"
+
+    def test_zero_padding(self):
+        """Zero padding on numbers."""
+        assert js_eval(py2js("x = 42; f'{x:05}'")) == "00042"
+
+    def test_zero_padding_with_sign(self):
+        """Zero padding preserves sign position."""
+        assert js_eval(py2js("x = 42; f'{x:+05}'")) == "+0042"
+
+    def test_width_no_alignment(self):
+        """Width without explicit alignment (defaults to right)."""
+        result = js_eval(py2js("x = 7; f'{x:3}'"))
+        assert len(result) == 3
+        assert "7" in result
diff --git a/tests/b_integration/test_dictcomp.py b/tests/b_integration/test_dictcomp.py
index e15ada3..99999db 100644
--- a/tests/b_integration/test_dictcomp.py
+++ b/tests/b_integration/test_dictcomp.py
@@ -38,15 +38,17 @@ def test_with_if(self):
         code = "{k: v for k, v in items if v > 0}"
         result = js(code)
         assert "if (!(" in result
-        assert "v > 0" in result
+        # Accept either native operator or runtime helper for unknown types
+        assert "v > 0" in result or "op_gt(v, 0)" in result
         assert "continue" in result
 
     def test_multiple_ifs(self):
         """Dict comprehension with multiple conditions"""
         code = "{k: v for k, v in items if k > 0 if v < 10}"
         result = js(code)
-        assert "k > 0" in result
-        assert "v < 10" in result
+        # Accept either native operator or runtime helper for unknown types
+        assert "k > 0" in result or "op_gt(k, 0)" in result
+        assert "v < 10" in result or "op_lt(v, 10)" in result
 
 
 class TestDictCompNested:
diff --git a/tests/b_integration/test_genexpr.py b/tests/b_integration/test_genexpr.py
index 9755336..de9abe1 100644
--- a/tests/b_integration/test_genexpr.py
+++ b/tests/b_integration/test_genexpr.py
@@ -44,15 +44,17 @@ def test_with_if(self):
         code = "(x for x in items if x > 0)"
         result = js(code)
         assert "if (!" in result
-        assert "x > 0" in result
+        # Accept either native operator or runtime helper for unknown types
+        assert "x > 0" in result or "op_gt(x, 0)" in result
         assert "continue" in result
 
     def test_multiple_ifs(self):
         """Generator expression with multiple conditions"""
         code = "(x for x in items if x > 0 if x < 10)"
         result = js(code)
-        assert "x > 0" in result
-        assert "x < 10" in result
+        # Accept either native operator or runtime helper for unknown types
+        assert "x > 0" in result or "op_gt(x, 0)" in result
+        assert "x < 10" in result or "op_lt(x, 10)" in result
 
 
 class TestGenExprNested:
diff --git a/tests/b_integration/test_lambda.py b/tests/b_integration/test_lambda.py
index 950a091..e51548b 100644
--- a/tests/b_integration/test_lambda.py
+++ b/tests/b_integration/test_lambda.py
@@ -105,7 +105,8 @@ def test_lambda_comparison(self):
         """Lambda with comparison."""
         code = "is_positive = lambda x: x > 0"
         result = js(code)
-        assert "(x > 0)" in result
+        # Accept either native operator or runtime helper for unknown types
+        assert "(x > 0)" in result or "op_gt(x, 0)" in result
 
     def test_lambda_boolean_expression(self):
         """Lambda with boolean expression."""
diff --git a/tests/b_integration/test_unpack.py b/tests/b_integration/test_unpack.py
index ccd6f58..5ce2646 100644
--- a/tests/b_integration/test_unpack.py
+++ b/tests/b_integration/test_unpack.py
@@ -66,17 +66,18 @@ def test_double_assign(self):
         """Double assignment a = b = 2"""
         code = "a = b = 2"
         result = js(code)
-        # Should declare both variables
+        # Should declare both variables with value 2
         assert "b = 2" in result
-        assert "a = b" in result
+        assert "a = 2" in result
 
     def test_triple_assign(self):
         """Triple assignment a = b = c = 3"""
         code = "a = b = c = 3"
         result = js(code)
+        # All variables should be assigned value 3
         assert "c = 3" in result
-        assert "b = c" in result
-        assert "a = b" in result
+        assert "b = 3" in result
+        assert "a = 3" in result
 
 
 class TestNestedUnpack:
@@ -119,3 +120,61 @@ def test_starred_middle(self):
         result = js(code)
         assert "pop()" in result
         assert "middle" in result
+
+
+class TestChainedSubscriptAssign:
+    """Tests for chained assignment with subscripts and attributes."""
+
+    def test_chained_subscript(self):
+        """Chained assignment with subscripts: a[0] = a[1] = value"""
+        from prescrypt.testing import js_eval
+
+        code = "a = [True, True]; a[0] = a[1] = False; a"
+        result = js_eval(py2js(code))
+        assert result == [False, False]
+
+    def test_chained_subscript_int(self):
+        """Chained assignment with subscripts using integers."""
+        from prescrypt.testing import js_eval
+
+        code = "a = [0, 0, 0]; a[0] = a[1] = a[2] = 5; a"
+        result = js_eval(py2js(code))
+        assert result == [5, 5, 5]
+
+    def test_chained_attr(self):
+        """Chained assignment with attributes: c.x = c.y = value"""
+        from prescrypt.testing import js_eval
+
+        code = """
+class C:
+    x = 0
+    y = 0
+c = C()
+c.x = c.y = 5
+[c.x, c.y]
+"""
+        result = js_eval(py2js(code))
+        assert result == [5, 5]
+
+    def test_mixed_chained(self):
+        """Chained assignment mixing names, subscripts, and attributes."""
+        from prescrypt.testing import js_eval
+
+        code = """
+class C:
+    x = 0
+c = C()
+b = [0]
+a = b[0] = c.x = 3
+[a, b[0], c.x]
+"""
+        result = js_eval(py2js(code))
+        assert result == [3, 3, 3]
+
+    def test_chained_dict_subscript(self):
+        """Chained assignment with dict subscripts."""
+        from prescrypt.testing import js_eval
+
+        code = "d = {}; d['a'] = d['b'] = 10; [d['a'], d['b']]"
+        result = js_eval(py2js(code))
+        assert result == [10, 10]
diff --git a/uv.lock b/uv.lock
index 0459edf..f0d0e8d 100644
--- a/uv.lock
+++ b/uv.lock
@@ -83,15 +83,6 @@ wheels = [
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-version = "0.22.9"
-source = { registry = "https://pypi.org/simple" }
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@@ -101,15 +92,6 @@ wheels = [
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-wheels = [
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-
 [[package]]
 name = "certifi"
 version = "2026.1.4"
@@ -460,60 +442,6 @@ wheels = [
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-    { name = "rich" },
-    { name = "typing-extensions" },
-]
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 [[package]]
 name = "pre-commit"
 version = "4.5.1"
@@ -1223,17 +1116,12 @@ wheels = [
 name = "prescrypt"
 version = "0.9.1"
 source = { editable = "." }
-dependencies = [
-    { name = "buildstr" },
-    { name = "plum-dispatch" },
-]
 
 [package.dev-dependencies]
 dev = [
     { name = "abilian-devtools" },
     { name = "attrs" },
     { name = "devtools" },
-    { name = "dukpy" },
     { name = "mkdocs-material" },
     { name = "mypy" },
     { name = "nox" },
@@ -1259,17 +1147,12 @@ doc = [
 ]
 
 [package.metadata]
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-    { name = "plum-dispatch", specifier = ">=2.1.1,<3.0.0" },
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 [package.metadata.requires-dev]
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     { name = "attrs", specifier = ">=23.1.0,<27.0.0" },
     { name = "devtools", specifier = ">=0.11.0,<1.0.0" },
-    { name = "dukpy", specifier = ">=0.3.0,<1.0.0" },
     { name = "mkdocs-material" },
     { name = "mypy", specifier = ">=1.19.1" },
     { name = "nox", specifier = ">=2025.5.1" },
@@ -1584,19 +1467,6 @@ wheels = [
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 ]
 
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-version = "14.2.0"
-source = { registry = "https://pypi.org/simple" }
-dependencies = [
-    { name = "markdown-it-py" },
-    { name = "pygments" },
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-wheels = [
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-
 [[package]]
 name = "ruff"
 version = "0.14.13"