Each turn, a player stacks one of his towers on a neighboring tower, but only if the targetted tower is smaller or of equal height.

Each of two players controls towers of one color. A tower is controlled by a player if his color is on top.

A turn in the game consists of moving a tower to one of its (max) 4 directly neighboring spots on the grid. The attacking tower is stacked on top of the attacked tower. A move is legal when the attacked tower is at most as high as the attacking tower. A tower may move to an empty neighboring spot.