Main problem is the controls. Maybe it's because it's a smartphone surface instead of buttons, but crouching in the right direction to do a spin dash was the most aggravating goddamn chore. Sonic kept turning around, or would step forward instead of crouching. Quit after playing three acts. Timing of some objects is off e.g. the blue gloop traps are faster than in the original game. I recommend only playing the free version to see if you think it's worth putting up with these annoyances. Definitely don't pay for it. I'm uninstalling after this review. Disappointed. Still got my sonic collection on xbox 360. Now that was a good purchase.