The physics aren't identical to the classic Sonic games, but I don't mind because the controls are fun anyway. I really like how much height you can gain by spindash jumping off of slopes, it reminds me of Sonic Adventure.
Biggest issue with the game is that the challenges aren't telegraphed. You can be running at top speed and a crusher just insta-kills you. It'd be better if they had some sort of tell, the way that Spring Yard Zone does in Sonic 1. That level had fast and slow sections, and the slow sections usually had roadblocks to kill your speed so you didn't run headfirst into the enemies/spike balls. The roadblocks were small enough that you could jump over them on repeat playthroughs and speed through the obstacles. Something like that would be appreciated here, especially if you add a lives system — getting a game over to something you couldn't even react to would be super frustrating.
Biggest issue with the game is that the challenges aren't telegraphed. You can be running at top speed and a crusher just insta-kills you. It'd be better if they had some sort of tell, the way that Spring Yard Zone does in Sonic 1. That level had fast and slow sections, and the slow sections usually had roadblocks to kill your speed so you didn't run headfirst into the enemies/spike balls. The roadblocks were small enough that you could jump over them on repeat playthroughs and speed through the obstacles. Something like that would be appreciated here, especially if you add a lives system — getting a game over to something you couldn't even react to would be super frustrating.