THIS GAME IS WAAAAAAAAAAAY OVERSCORED!
It scored almost a 4 average when it's missing many elements!
It's only a demo so I see why it may be a little plain. BUT ITS WAY OVERSCORED! PPLE, DONT GIVE CREDIT FOR THE SOUND IF THERE IS NONE! I'm positive this took you less than an hour to make.
Otherwise i'll start with the real advice:
1. Sonic has one pose and the animations are crudy.
2. there is 1 type of enemy.
3. Make it sonic like, with sonic characters and sonic levels.