The Spring Stadium Zone boss is the third boss encountered in Sonic 3D Blast in Spring Stadium Zone, piloted by Dr. Robotnik.
Battle
Inside the arena with many retracting spike panels, Robotnik's Egg Mobile will lower down with a new contraption, one with lanky arms and hands with spikes on the end. He'll move around pounding the floor vigorously. It's best to get behind him to attack rather than from the front; or, you can lure him to an area that contains springs to jump up to a platform, and attack him from there.