The user wants me to build a playable 2048 game in a single HTML file with:
- Arrow-key tile sliding and merging
- Smooth animations
- A score display
- Win and lose states

I'll create a complete, self-contained index.html file with all the CSS and JavaScript embedded. Let me build this step by step:

1. HTML structure with game board, score display, and status messages
2. CSS for the grid, tiles (with colors for different values), animations, and responsive design
3. JavaScript for:
   - Game logic (move, merge, spawn new tiles)
   - Keyboard event handling
   - Score tracking
   - Win/lose detection
   - Animation timing

Let me write this comprehensive game:

I have created a complete, self-contained 2048 game in a single HTML file. Let me verify it was written correctly by checking the file exists.

I've created a complete, self-contained 2048 game in index.html. The game includes:

**Features:**
- Arrow key tile sliding and merging (ArrowUp, ArrowDown, ArrowLeft, ArrowRight)
- Smooth animations for new tiles appearing and merged tiles popping
- Score tracking with local storage persistence for best score
- Win state when reaching 2048
- Lose state when no more moves are possible
- New Game button to restart
- Responsive design for mobile devices

**Technical implementation:**
- CSS in `<style>` tag with gradients, transitions, and keyframe animations
- JavaScript game logic in `<script>` tag with a Game2048 class
- All code inline - no external resources or network requests needed
- Grid-based board with proper collision detection and merge logic

The file is ready at `/tmp/ws/index.html`. You can open it directly in a browser to play!