I think you have a decent idea for this game, though the randomness & level design is what threw me off. Sometimes I would wait at a platform for the right keys to appear and they just wouldn't. Instead of giving the player random keys to use, you could manually add a list of keys (looping) and use that to design interesting situations.
I also didn't realize you could hold a key down at first. If you had better visual feedback for when you were holding onto a key, it would be more obvious.