Make the balls bounce on the side coincident with their color to make them vanish; the special grey balls can be sent anywhere. If a ball hits the wrong side you lose a life. Hit the walls close to the middle to earn more points. Every time the same ball bounces, a score multiplier is applied, to a maximum of 5 (the multiplier is indicated by a darker circle inside the ball).
Move the mouse to move to left/right. If you keep the mouse button pressed, the shot will be stronger enabling you to regulate how high you throw the balls. As you progress in the game you'll see new stuff, you should proceed by trial and error to discover all the secrets of the game.