2048

How to play: slide the whole board with the arrow keys, a swipe, or the buttons under it. Tiles glide as far as they can, and two tiles of the same number that collide join into one worth their sum — each merge pays that sum in points, and a tile only merges once per move. Every move that shifts something drops a new tile on an empty cell: a 2 nine times out of ten, otherwise a 4. Make a 2048 tile and the game is won — you can keep playing for a higher tile. When the board is full and no neighbouring pair matches, the game is over.