It's good! Faithful, accurate, fun. Sand Shower/Dust Hill/Whatever Sand Zone was fun and also probably the best interpretation of it I've seen to date, with the cactus bomb enemies being a nice surprise, and the giant ring system returning from Sonic 1 was also pretty nice, but aside from that, there's nothing I can really say - Emerald Hill was almost identical to the original, and the differences seem to be intentional things inspired by the prototypes, the game controls like Sonic 2, looks like Sonic 2 and sounds like Sonic 2.