I tested your demo, it's a great work.
Don't worry about the steam's comments,they forget that limbo is also a clone (example:world of goo( for physic)+ dark theme ).
I noted the following things:
- when up arrow (or z or B button) is down, the player jump in the air (and not on the floor)
- the left analog y axis is too sensitive for the jump (i think) ("gamepad left analog y axis < 25" ?)
- on controle menu, grap and jump have both Z key (annoying)
- i love the trap after the ball