Implement interactive video player with checkpoint-based exercises for kids English learning platform

[Copilot]

Implements US-S003: Interactive video lessons that pause at predefined timestamps to present vocabulary, quizzes, and pronunciation exercises.

Architecture

InteractiveVideoPlayer class wraps HTML5 video with checkpoint-based pausing:

• Monitors timeupdate events to trigger checkpoints at specific timestamps
• Overlays exercise UI on pause, resumes on completion
• Persists progress to localStorage (backend integration ready)

const player = new InteractiveVideoPlayer(videoElement, lessonData, {
  autoplay: false,
  showControls: true,
  enableSubtitles: true
});

Exercise Types

Three checkpoint types implemented:

• Vocabulary: Word + pronunciation + definition + image + examples
• Quiz: Multiple choice with instant feedback, auto-advance on correct answer
• Pronunciation: Audio playback + recording placeholder (speech API ready)

Data Models

• Lesson: Metadata + checkpoints array with timestamps
• Checkpoint: Type-specific data (vocabulary, quiz, pronunciation)
• StudentProgress: Completion tracking + score + badges

Progress & Achievements

• Save/resume via localStorage (methods ready for API integration)
• Scoring: 10 points per correct answer
• Star ratings: 1-5 based on accuracy percentage
• Badge system: first lesson, 5 lessons, perfect score

Sample Content

Three lessons with 16 interactive checkpoints:

1. Greetings & Introductions (5 min, 5 checkpoints)
2. Colors & Shapes (6 min, 5 checkpoints)
3. Animals & Sounds (7 min, 6 checkpoints)

UI/UX

• Child-friendly controls and feedback (large buttons, emojis, animations)
• Responsive CSS (tablet + desktop)
• Accessible (ARIA labels, keyboard nav)
• Playback speed control, subtitles, fullscreen

Integration Points

Ready for:

• Any HTML5 video source (Azure Media Services, Vimeo, etc.)
• Speech recognition API (placeholder in recordPronunciation())
• Backend storage (replace localStorage calls in saveProgress()/loadProgress())
• Analytics service (event logging via logEvent())

Files

kids-english-learning/
├── src/
│   ├── interactive-video-player.js  # Core player (21KB)
│   ├── lesson-data.js               # Models + samples (13KB)
│   └── styles.css                   # Complete styling (10KB)
├── examples/demo.html               # Working demo
├── tests/video-player.test.js       # Unit tests
└── docs/                            # Documentation

Original prompt

---

This section details on the original issue you should resolve

<issue_title>implement user story</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

@jacwu @foundry get the detail of user story “US-S003: Interactive Video Lessons” of the kids english learning platform

• Fixes implement user story #35

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