Press space to start. Use the arrow keys to control the slime. Space won't work for jumping; it will work for starting up the program, so if you panic because the arrow keys don't work, press space! Reminder that it's a WORK IN PROGRESS, so it's very easy right now. All levels are not tested... I couldn't do it myself... So if you do it, put it in the comments and I mention you in the instructions. Only the first five people are put in.
Most of the credit goes to mg191101137, for making it. I just made it a bit easier. If you like this, check out Impossible Platformer 1.1A.