The special stages needs to be tweaked, the speed at which things comes at me throws me off every time, and the physics feels very wrong there. Outside the special stage, the physics feels nice and responsive.
For the Special Stage, I think it might be a good idea to look at Sonic Rush's or do something entirely new, like a more plain area where you move left, right and jump to dodge obstacles. Oh, and add a ring requirement to the screen (like showing X/30, X/60).
Keep up the real nice job! Glad someone like you is remaking 3D Blast in an actually fun environment.