I know there is no mobile version, but I've been playing it on JoiPlay with extremely low FPS. Still, I'm having fun.
I don't know why the FPS drops so much, because I can play other games—like Karryn's Prison—at 60 FPS. Is there something different in the way it's programmed in Game Maker?
For your first question the mysterious key has no use in the demo. It's simply a teaser item.
As for JoiPlay, anything related to it is completely out of my control so I can't really speak to any performance issues encountered through using it. On my PC the game runs at a pretty consistent 60 fps. My 12-year-old Mac laptop is closer to 20 but I've personally never even tried it on a phone, nor did I build it with that really in mind.
