Space Commanders

As a Space Invaders clone, your task in this game is to defend the Earth against endless waves of incoming aliens. The more you kill, the faster they go; if they complete their winding descent down the screen, your mission is over. Each row in the orderly squadrons is populated by a distinct breed of vaguely-insectoid intruder, and their point values vary accordingly – you get less for zapping the cannon-fodder at the bottom, more for the higher-ups. If you get them all, a new batch of uninvited guests will drop by for another (more difficult) round.