I had a blast playing it. It had character, some new badniks, a cute butterfly following you around, good music, and enjoyable levels. Don't get me wrong when I say this, but it definitely feels like a fan game and not like an original SEGA game, it reminded me a lot of Sonic Axiom at times with the rings in arrow shapes. I wasn't necessarily a fan of the custom shield(s?) though.
I used an Xbox One controller and the D-pad didn't work, I needed to use the analog stick, but it was fine. Might be worth looking into.
I think the tile sprites need some work, the grass looks a bit too simple and you need some fills to break the pattern in the blocks, similarly to how Green Hill, Palmtree Panic or Mushroom Hill would do it. But you can try other things as well like other levels would do. I liked the burnt palette change in the end of Act 3, it worked well.