Nifty.
Great graphics and sound lifted from the games, a decent level design, everything in this game feels like sonic. The move list is limited but what's there works well, and it was fun to see how many times I could bounce off of Robotnik's head without falling to the ground. However, collision detection with wall and ground is on the poor side, and it's possible to jump off the left and right boundaries of the level and fall forever. You really should've programmed Sonic to just die after falling a certain amount of time or something like that.