Fun game! It has a lot of potential. I absolutely love the grotesque aesthetic and ambience, the audio and the visuals along with the retro style fits really well the theme.
Personally, I would love to see the spin-attack be fused with the jump mechanic, it feels a bit redundant to have an attack button when I can do that and move using the jump button. I believe it can also help the game feel more like its own thing and less of a 'sonic inspired game' (which isn't necessarily bad, but would make it more unique).
But that's just a suggestion. Great job guys!