Microbe is a fixed screen shoot the alien invader game with a difference in that the action is played out within the alien. The player takes control of a microbe inserted into the alien and must destroy the various cells, antibodies, aminos and spores inside the alien. The microbe can be moved left and right but also up and down. Each level has its own enemies with its own appearance and movement pattern. In addition to blasting away at the enemies the player also has to watch out for the projectiles that they drop. The player has three lives and when they are used up the game is over. Microbe was inspired by Myriad for the VIC-20 with similar gameplay although without the micro-organism theme.