The boss of Quartz Quadrant is the fourth boss encounter in Sonic the Hedgehog CD. Once again found in the third Zone of the level, the Quartz Quadrant fight is just as much a part of the room Sonic the Hedgehog enters as it is the machine Dr. Eggman is standing in. While most of the bosses in the game require timing and precision in hitting Eggman's latest contraption, this is one of the handful of times in which Sonic's patented spin attack is of no use.
Needing to hit the piston Eggman is standing in to start up the battle, the actual fight roars to life, the mad doctor's mechanical creation lowering onto the conveyor belt below. With the entrance to the room now blocked off by a dangerous bed of spikes, any subsequent hit against the piston is an exercise in futility. Instead, Sonic must concentrate on staying alive in this encounter, running ahead to avoid the spikes and also dodging the bombs dropping from the ceiling. Stopping only when above the hedgehog, the single bomb falls to the ground, exploding into four smaller, spiked projectiles. While possibly easy to avoid on their own, the combination of the conveyor belt trying to drag Sonic to the spikes on one end and the small enclosure of the fight makes it all the more dangerous.
However, the boss is not without its weakness, that being itself. Eventually, the friction caused by the piston rubbing against the conveyor belt will cause the machine to start melting, the process exponentially sped up by having Sonic the Hedgehog running on the belt towards Eggman. Though Sonic can never touch the machine while running, the hedgehog's namesake causes the melting to speed up, until finally Eggman is forced to dance about, the heat seeping into the soles of his shoes. With sparking metal and glowing slag, the genius doctor is eventually forced to abandon his machine, running away from Sonic as the machine begins to explode. With another simple hit of the seed-filled capsule, Sonic continues his journey across the face of the Little Planet into Wacky Workbench.