Hello guys,
TLDR: HELP ME COME UP WITH A CORE GAMEPLAY MECHANIC

I've been developing this little platformer as a sideproject for a few months without any core gameplay design in mind. I just built and added new random things as I went along and I assumed I would run into an idea at some point. Now I'm at a point where I need to come up with some core gameplay mechanic but can't come up with anything great.
The game is now developed as a mobile port (that's what the buttons are for). Any input …