In Klustar, you control a magic block being inundated by shapes of various block configurations that appear from the sides of the screen. These blocks stick to your block and form a klustar, which you can rotate clockwise and counterclockwise. The goal is to keep your klustar as small as possible by fitting blocks together to form squares of at least 3 x 3 blocks. Once these square matrixes are created, they disappear. Shapes that do not attach to the klustar build up on the edges of the screen. Gameplay continues until your klustar becomes so big that it touches the sides of screen or cannot move, or when there is no room for shapes to enter the screen.