Scrap Brain is the toughest zone in the game. It is an electro-mechanical death-trap which is Robotnik's favourite hangout. Being the last zone just about everything is used to kill. It is full of platforms which can only be stood on when they are not rotating, holographic steps that appear and disappear after a few seconds, conveyor belts and transport tunnels.

Just about everything in this zone is lethal; a few are bottomless plunges, electrical blasts from generators sometimes on the floor or ceiling, buzz saws with some of them not attached to anything and racing across the floor, igniting gas from broken pipes and the smart exploding mines.

Act 1	Act 1
Act 2	Act 2
Act 3	Act 3

There is a slight intersection between acts 2 and 3. Robotnik appears behind a force field and sends Sonic for a swim underneath Scrap Brain Zone. The grimy factory landscape is replaced in act 3 for a Labyrinth Zone style course.