Well, the game is not completely zero, it even has some passages quite nice, but this game collects faults: - Some passages are poorly explained or indicated, suddenly we lose because of the timer (ranging from 15 to 30 minutes depending on the level) - Handling is often very rough - Others are aberrant and difficulty totally free (you know, the kind of way where you lose all your lives in less than 30 seconds each) - The video quality is poor, even for 3DS - Chaos emeralds levels are played ONLY in gyroscope. I can understand that some appreciate this type of controls, but then to make it mandatory, it's just not. It got to the point where I preferred not to these levels when you proposed to me.
In short, I formally recommend, if you want a good platform game on 3DS will instead see Mario 3D Land or Sonic Generations if you are looking for a absolutely Sonic, but certainly not this title.