Keep colored balls on fields of corresponding color, and away from fields of different colors.
Controls: mouse only. Grab white ball with your mouse. Push colored balls with the white ball to the corresponding colored fields and away from differently colored ones. Black balls just make it harder. If you keep colored balls on fields for a preset time, you proceed to the next level. Hint1: push gently. Hint2: pushing black balls can be as productive as pushing colored ones.