Select your character from amongst 4 Sonic the Hedgehog stalwarts including: Sonic (obviously), Amy Rose, Dr. Robotnik, and Knuckles. There doesn't appear to be any difference to selecting one character over another other than the cosmetic flavor. The game is very simple but you do have to be sure to lean left/right at the right time after jumping to avoid slowing down.
How to play
Up/Down Arrow: Gas/Brake Left/Right Arrow: Left/Right P: Pause