Just tried it out myself. Hate to be a bit harsh, but the game just seemed annoying to me..
1. I don't know about anyone else but the stripe design on the ground really bothered my eyes... and looks really ugly IMO.
2. I like the Crab badnik but I think there was waaaay too many and I consider it really annoying not only for constantly bumping into one every few seconds, but for being the only real challenge in the whole demo.
3. Didn't like the level layouts so much..found them to be really short and bland with a lot of slopes. I suggest more gimmicks and more alternate paths.
4. The boss was incredibly easy & repetitive plus took too many jumps to kill. Although, almost all 1st bosses in sonic games are like this so I suppose you'll slide. However I would suggest adding another attack pattern for it.
The game does has potential, don't get me wrong but it needs a lot of work.