Arrow keys or WASD to move, up arrow or W to jump, and note the this is a demo. It is very likely that you will get stuck in the floor, so press R to reset. That's all!
HUGE thanks to @-Rocket- for the scrolling code!!! I could not have done this without your project! I had tried SOOOOOOOOOOOOOO many scrolling thing and, believe it or not, this is the only one that actually works! lol. Oh yeah, and ALSO, a big thanks to @Reptlow for the Sonic sprites and title screen sprites! I'm too lazy to make my own. :P