Aliens have invaded planet Earth and it is up to you to destroy them all. You and your troops have set up a base and your ultimate goal is to protect it at all costs. You must remain on the base at all times. Underneath the base are fuel tanks that you should avoid hitting. Through out the game play you may have to re-position your soldiers and also re-positioning the direction of their gunfire. Pick up packages and bonus' that fall from the sky. Stars are an extra 100 points but they disappear quickly. Also, do not let your soldiers fall off of the base.