2048

Goal

Slide all the tiles at once. Two tiles of the same value that meet merge into one, with double the value. Reach the goal tile (2048 at Medium level), then carry on if you like to aim higher.

How it works

• Swipe the board, or use the keyboard arrow keys (or W, A, S, D).
• After each slide, a new tile appears in an empty square: a 2 nine times out of ten, otherwise a 4.
• A tile only merges once per move: 2, 2, 2, 2 gives 4, 4.
• Each merge scores its value in points.
• The game ends when no slide is possible any more.
• The tiles change material as they grow: porcelain, enamel, brass, then neon glass beyond 2048.

Levels

• Easy: 5 × 5, goal 2048.
• Medium: 4 × 4, goal 2048 (the classic game).
• Hard: 4 × 4, goal 4096.
• Expert: 3 × 3, goal 512.
• Devilish: 4 × 4 with an immovable cast-iron tile on one of the four central squares; tiles stop against it and can neither pass through it nor merge with it. Goal 2048.

About the AI

The autopilot uses an expectimax search: it tries its four slides, then every possible spawn of a 2 and a 4, weighted by probability, several moves ahead. Each position is evaluated by a heuristic (empty squares, upcoming merges, monotonicity of rows and columns) precomputed for every possible row; a transposition table avoids re-evaluating positions already seen and branches that are too improbable are pruned. The depth adapts to the time available. On the classic 4 × 4, it reaches 2048 in the vast majority of games and often carries on to 4096 or 8192.

Undo also restores the random draw: replaying the same move makes the same tile appear. Records are only registered without undos, hints or autopilot.