Arrow keys to move. Jump on the monsters to kill them. Collect the key to unlock the door in room 5. It is unfinished right now. See if you can find and access the "Lost Levels" in your own remix. There are three of them. Here's a hint. Delete the walls...
Thanks to @griffpatch and @griffpatch_tutor for providing videos and resources on how to do this. You are great, griffpatch.