The aim of the game is to eliminate all of the falling orbs with the use of your cursor zapper and base zapper (controlled by the A, S and D keys on your keyboard).
The orb shown in the square box at the bottom of the screen is the orb you should zap with your base zapper, other orbs you should click to destroy with your cursor zapper. Careful not to mix these up or you'll lose lives. You'll also lose lives if you fail to zap or catch a falling orb.