Round green plates appeared in the sky, at first there were several of them, and then the number began to increase sharply and you should think about how to start defending yourself. Extend the flying cannon and go towards the alien invaders. They have already begun to shower you with a hail of rockets, from which you need to dodge, you control the gun and can move in a horizontal plane. Go through the levels in Alien Invaders 2, destroying all the alien ships, do not let them land.
