Snake Game

# Snake Game PRD

## Overview
Build a classic Snake game playable in the browser.

## Requirements
- Canvas-based or DOM-based rendering
- Arrow key controls (WASD also accepted)
- Snake grows when eating food
- Game over on wall collision or self collision
- Score display (1 point per food eaten)
- Speed increases every 5 points
- High score saved to localStorage
- Start screen with "Press ENTER to start"
- Game over screen showing final score and high score
- Pause/resume with Spacebar
- Grid-based movement (not free-form)
- Clean, retro-styled visuals

## Tech Stack
- Vanilla JS with HTML5 Canvas, or any framework
- No backend required

## Scoring Criteria
- **Functional (40%)**: Game loop works, collision detection, scoring, speed increase
- **Quality (20%)**: Smooth rendering, no flicker, clean code
- **Fidelity (25%)**: All features present, good game feel
- **Speed (15%)**: Time bonus