Mainframe is perhaps one of the hardest levels in the entire 00 column, thanks to the homing turret commanding the entire level, various patrolling zap drones, gauss turrets, and that accursed doorswitch chamber designed to lead you around the entire level dodging all those threats. This level is so named because it resembles a giant brain, specifically, Mother Brain, from the Metroid series. Planet Zebes's "mainframe"