You must defend the 10 planets from the vectors using the base gun. You will initially be defending one planet at a time and after every successful defense, you will be able to unlock another planet. You should use the mouse to play this game. You use the mouse to aim, click and hold to gain power and release at the right time to shoot at an object. Remember that Red blockers on later levels cannot be destroyed. You can destroy the satellites passing along your screen to gain new weapons for a short period of time. You could rebound your bullets of multiple enemies for higher scores.