Egg Conveyor
From Sonic Retro
The boss of Quartz Quadrant is the fourth in Sonic CD. As with most of Robotnik's boss machines in this game, the Quartz Quadrant fight is heavily tailored to the battle arena. In this case, the confrontation takes place on top of a spiked conveyor belt, with Robotnik ensconsed in a piston-like control module - like some sort of hybrid between the Gene Gadget Zone boss and Final Zone.
After clocking Robotnik's pod with a single hit, the Doctor's position drops down to rest on the conveyor belt - which then starts up. It is impossible for Sonic to land other hits on the fat man during this boss; the hedgehog must instead simply concentrate on staying alive, keeping away from the spikes at the left of the belt, and the exploding bombs which periodically get dropped from above. The boss is eventually self-defeating; as time goes on, friction begins to visibly wear down the underside of Robotnik's module, throwing up sparks and turning the metal to glowing slag until Robotnik begins to dance as the heat seeps through his shoes. Finally, the obese scientist abandons his position and runs away, allowing Sonic to proceed to Wacky Workbench.