Klustar is a puzzle game for the Game Boy Color in which players control a magical block inundated by incoming shapes from the screen's edges. The objective is to form a compact klustar by rotating and fitting blocks together to create squares of at least 3 x 3 blocks, which then disappear. The game ends when the klustar becomes too large or when shapes can no longer enter the screen.
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.