In this game there is a grid of balls that are slowly moving down. You need to shoot balls to destroy them by forming groups of 3 or more balls of the same colour.
After you have destroyed some balls, the balls that are not attached the the rest of the balls will fall down and be destroyed.
Sometimes you may need to shoot the balls to the wall so that they bounce off and destroy other balls. If you cannot destroy all the balls before they reach the bottom of the screen, you lose.