week15.py

# Week 15: Catch the Stars (Collision Detection + Score)
# Goal: Implement collision detection and scoring
# New concept: ERROR HANDLING with try/except

import random

WIDTH = 700
HEIGHT = 500

# Player position (using list for [x, y])
player = [WIDTH//2, HEIGHT//2]
speed = 5

# Star position
star = [random.randint(20, WIDTH-20), random.randint(20, HEIGHT-20)]
score = 0

def distance(a, b):
    """
    Calculate distance between two points.
    Uses Pythagorean theorem: √(dx² + dy²)
    
    Args:
        a: [x, y] position of first object
        b: [x, y] position of second object
    Returns:
        Distance in pixels (float)
    """
    dx = a[0] - b[0]
    dy = a[1] - b[1]
    return (dx*dx + dy*dy) ** 0.5  # ** 0.5 is square root

def respawn_star():
    """Move star to new random position"""
    star[0] = random.randint(20, WIDTH-20)
    star[1] = random.randint(20, HEIGHT-20)

def update():
    global score
    
    # Player movement
    if keyboard.left:  player[0] -= speed
    if keyboard.right: player[0] += speed
    if keyboard.up:    player[1] -= speed
    if keyboard.down:  player[1] += speed

    # Boundary checking
    player[0] = max(10, min(WIDTH-10, player[0]))
    player[1] = max(10, min(HEIGHT-10, player[1]))

    # NEW CONCEPT: ERROR HANDLING
    # Sometimes distance() might fail - let's handle it safely
    try:
        # Collision detection - check if player touches star
        if distance(player, star) < 20:
            score += 1
            respawn_star()
    except Exception as e:
        # If something goes wrong, print error but keep game running
        print(f"Collision check error: {e}")

def draw():
    screen.clear()
    screen.fill('darkblue')
    
    # Display score
    screen.draw.text(f"Score: {score}", (20, 20), color='white', fontsize=30)
    
    # Draw player (white circle)
    screen.draw.filled_circle(tuple(player), 10, "white")
    
    # Draw star (yellow circle)
    screen.draw.filled_circle(tuple(star), 8, "yellow")

# === KEY CONCEPTS ===
# 1. Lists for positions: player[0] = x, player[1] = y
# 2. Distance formula for collision detection
# 3. try/except for error handling (new!)
# 4. tuple() converts list [x,y] to tuple (x,y) for drawing
# 5. Collision threshold: distance < 20 means "touching"