feat: initial commit of Railtrack Pro prototype with complete test suite

PLAN.md

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+# Railtrack Pro - Development Plan
+
+## Project Overview
+A web-based railway construction game featuring track building, junctions, signals, and 3D driver's eye view.
+
+## Features
+- 🚂 Track pieces (straight, curved, junctions, signals)
+- 🌍 World grid system for track placement
+- 🎮 Interactive construction interface
+- 👁️ 3D Driver's eye view
+- 🔌 Junction and signal logic
+- 💾 Save/load game states
+
+## Architecture
+```
+/railtrack_pro/
+├── index.html          # Main HTML structure
+├── css/
+│   └── styles.css      # Application styles
+├── js/
+│   ├── app.js          # Main application logic
+│   ├── renderer.js     # Three.js renderer
+│   ├── tracks.js       # Track piece definitions
+│   ├── world.js        # Grid and world management
+│   └── game.js         # Game state and controls
+├── assets/
+│   ├── textures/       # Track textures
+│   └── models/         # 3D models
+├── test/
+│   └── unit/           # Test files (TDD)
+└── README.md           # Project documentation
+```
+
+## Technology Stack
+- **Frontend**: HTML5, CSS3, JavaScript ES6+
+- **3D Rendering**: Three.js
+- **Build**: No build system (vanilla JS)
+- **Testing**: Jest or Mocha for unit tests
+
+## Development Phases
+1. **Phase 1**: Basic project structure and HTML layout
+2. **Phase 2**: Three.js renderer setup with camera and scene
+3. **Phase 3**: Track piece system with placement
+4. **Phase 4**: Grid and world management
+5. **Phase 5**: Junctions and signals logic
+6. **Phase 6**: Driver's eye view feature
+7. **Phase 7**: Game state save/load
+8. **Phase 8**: Testing and documentation
+
+## Next Steps
+- Create project file structure
+- Set up Three.js renderer
+- Implement basic track pieces
+- Build placement interface
+
+---
+*Generated: 2026-03-13*