Welcome to the distant year 2850 and the game alien defense will send you there. Progress has reached unprecedented heights, but wars are still shaking our planet, and this time the enemies came from distant hostile galaxies. On their flying saucers, the aliens attack the Earth. They need to land in order to launch a massive offensive and exterminate the human race at the root. But you won't let them do this in alien defense. Your cannon is loaded with a myriad of charges. Just aim at the alien ships and they will be shot down. Do not let any of them reach the surface of the earth, otherwise defeat cannot be avoided.