2048

Swipe or use the arrow keys to slide every tile one way. Two tiles with the same number merge into their double and add that number to your score. A new tile appears after each move; the game ends when nothing can move. There is no timer - get to 2048, then keep going.

Every swipe slides all sixteen cells the same way at once, as far as they will go. Two tiles with the same number that bump into each other become one tile with double the number, and that number is added to your score.

A tile can only merge once per swipe. A row of 2 2 2 2 becomes 4 4, never 8 - so the big tiles are earned one swipe at a time.

A new tile appears after every swipe: usually a 2, occasionally a 4. If a swipe would not move or merge anything it is not a turn at all - nothing slides and no new tile appears, so a wasted swipe costs you nothing.

The game ends when the board is full and no two neighbours match. A full board is not the end on its own - if there is still a merge anywhere, there is still a move.

There is no undo. That is on purpose: a score you could take back would not be worth chasing. There is also no timer, so take as long as you like over a move.

Reaching 2048 does not stop anything. Keep going - 4096 is the next one.

Touch: tap anything on the board to use it. Every button and key is at least 44px tall, so it works with a thumb. The squares of a board are as big as the screen allows - on a small phone some of them are smaller than that, which is why the keys and the number pad, not the squares, are what you type with.

Keyboard: Tab moves between the controls and Enter or Space activates the one you are on. That covers the buttons the game screen always has - Pause, Restart and this page's link - as well as anything the board adds.

Pause stops the clock and freezes the board; Restart gives you a fresh one.

Your score is the points you have when the game ends. Higher is better.

Play as often as you like. Every game is saved on this device, and your best turns up on the scoreboard.