Destroy the alien ship before it reaches Earth! Move around using the arrow keys, and press Spacebar to plant a bomb. When it blows up, it will destroy everything in its radius, including you if you're too close. Destroy every enemy in the level, and then find the box with the exit underneath it to pass the level. The aliens aren't stupid, though. They'll do everything they can to run away from the bomb, so try to corner them. If you're lucky enough to find a remote-controlled bomb, press Enter to set it off.