The best genesis game made... ever!
Ingame, the main way you deal with enemies is to jump on them, or spin up to them if they are spiky on top. However, new power shields in the game also give you new ways to fight enemies, (but only when you play as sonic). Ex: If you double jump whilst you have the fire shield, you will become a fire ball and charge forwards at mega high speed. This also protects you from all fire attacks.
The graphics in this game are totally impressive. Whilst some genesis games are blurred and look kind of cheap, sonic 3 features crisp graphics and smooth framerate. This makes the game look and feel great even today.
Another cool feature is this game's adaptability. You can insert this game into the game "sonic an knuckles" to combine the 2 games into 1 giant extended game! This is cool because it is the only way to get all 14 chaos emeralds (7 normal and 7 super emeralds which are much harder to get.). You can also use knuckles for the sonic 3 levels and tails for the sonic and knuckles levels. This is the only way to access some of the less known secrets.
Bottom line: If you don't have a genesis, just get the ps2 sonic collection!