As with all his games, no instructions are given and the gameplay is only revealed gradually. The game takes place in an abstract, side-scrolling world where a character can be controlled. In the distance, a shimmering image of a tower is shown. It consists of blocks, each with a different squared pattern of colours. The aim of the game is to build the tower according to the pattern, but it is impossible to complete it without the help of the other player who has the same goal, but who is not visible on the player's screen.
The game consists of three different states, and they can be chosen by going to sleep or waking up, represented by an area on each side of the screen. The player starts with an outlined construction area where the patterns of blocks can be selected and built, to be moved to the tower where they are stacked. The player however starts with three colours: red, green and blue, while higher parts of the tower with complex colours include cyan, magenta and blue. These block patterns cannot be built by the player, but need to be provided by the other player. The other one however does not sees the player's tower and as such the correct patterns are created by accident, or it may just as well never happen, leaving the player unable to complete the game.
When a part of the tower is completed, a soft sound can be heard. When the game is played by two players in the same room, this can serve as an additional hint for the other player, as the author discourages looking at another player's screen.