Klax features a conveyor belt at the top of the screen. It constantly rolls toward the well-like playing area, delivering a steady supply of colored blocks. The player controls a small device which sits at the interface between the conveyor belt and the playing area. By moving this left and right, the player can catch the blocks and deposit them in the playing area. Failure to catch any block results in it falling down the gap between the conveyor belt and playing area and one drop being used. Once all of the drops are used, the player is given a chance to continue. Otherwise, the game ends.