There is a picture made of balls at the center of the field. At the field edges - up, down, right and left - are located the balls to shoot with. Select any ball from the row closest to the field and click on it. It will move along straight line until it bumps into another ball or the field edge. If, after that, the balls of the same color appear next to each other, they will disappear. Shoot to make all the balls on the field disappear. The game time is unlimited, but the complexity grows with the levels.