Aliens have invaded earth and decided to conquer your island as their first target. So you have to do your best and shoot them down with your cannon. The number of enemies will increase as you progress and they will become more powerful. Some enemies will drop power ups when destroyed and you need to collect these if you want to survive. These power ups are grenades, extra lives and an attack chopper. Grenades and attack chopper can help you in destroying aliens’ flying saucers and extra lives will make you to be able to withstand more hits from enemies. You will lose if you run out of lives and then your final score is calculated.