I like the shinyness of the logo and emblem a lot. Awesome game page background, by the way!
This game had a LOT more stages and mechanics than I anticipated. Some very cleverly designed levels, some slightly frustrating. As a fellow Sonic 1 and Sonic 4 player, I was very familiar with the special stages used as inspiration for the game, and the variety of the challenges present in this game surprised me a lot!
One thing that stood out to me is: in the first stage in which you need to actually "kill" an obstacle to progress, it didn't hit me that that's what I was meant to do until wandering around the stage a few times. It was because I thought those were a type of spike ball themselves, where I thought their only purpose was to damage me. Having some sort of indicator on the introduction to this mechanic would be nice.
What would help with that is having these enemies react to when you hit them by maybe having them flash, accompanied with a sound effect. It would help to point out that those objects are actually reacting to being hit, and they're not just taking some of your health, like an obstacle would.
This also applies to another stage in which the camera follows the enemy, and you have to hit them a few times. It was an extremely clever concept (especially with the giant cross the player gets so that you can always tell where you are), but at the first couple of times, I didn't know if that was what I was meant to do, since it didn't seem like the enemy was being affected by my hits.
The music was very nice, so it saddened me when it stopped looping. The sound effects were very fitting, and the instant reset button was really appreciated!
This is really impressive for a first game jam game. A lot of content here, and it's quite well put together! It impressed me a lot and I had a good time with it. A very clever game. Well done!