Great. Only a 2-player-simultan mode is missing. Would be a good idea for "Lets invade 3". Or, even better, a 4-player-simultan mode, playable with a 4-player-adapter. Would be much going on then on the screen, when 4 player-ships at the same time drive around to defend the earth. Sprites must be made smaller then, also the enemies. But i could imagine, how much fun this could be to play. :)