Swipe on the board in any of six directions and every tile slides that way. When two tiles with the same number meet, they merge into one. Six directions open up merges a square board never could, and they let tiles pile up from every side. Keep merging until you build a 4096 tile.
Q↖W↑E↗
A↙S↓D↘
On a keyboard, the six keys around W and S match the six ways a hex can move. ↑ ↓ work too, ← → go up-left and up-right, and with Shift down-left and down-right.