Game goal & end conditions

Goal: combine tiles to create the 2048 tile.
Win: when a tile reaches the value 2048.
Lose: when there are no valid moves left (no empty cells and no adjacent tiles with the same value).
How moves combine tiles:
- When you move (arrow key or button), all tiles slide in that direction as far as possible.
- If two tiles with the same number collide during a move, they merge into a single tile whose value is the sum of both (for example, 2 + 2 => 4).
- Each merge increases your score by the value of the new tile (e.g., merging two 4s into an 8 adds 8 points).
- Only one merge per pair of tiles is allowed each move (merged tiles do not merge again in the same move).

Game Over!

🎉 Congratulations! 🎉