The Galactic Plague is an alien shoot up in the vein of Galaga. In this version each screen has between 4 and 20 alien craft of differing variety. Each variety of alien moves in a different pattern but always down and usually at a rate of knots, dropping bombs as they do so (often just one enemy can blanket the screen in bombs, almost inevitably causing the demise of the player). The ship controlled by the player is confined to moving along the bottom of the screen. The secret of progressing in the game was therefore learning the patterns of the aliens and learning where to place the ship to shoot down the various hordes without getting crushed by the hundreds of dropped bombs or colliding with an alien as it hit the bottom of the screen, where it just wrapped around to reappear at the top.

The player only has three lives and many players found this game to be extremely difficult if not completely impossible after just a few screens, however, the game is completable. There are approximately 50 different screens and upon beating the last wave of enemies, the game goes straight back to screen No.1.