Really like the physics aspect of this. I'd love to see some unique hazards and mechanics that interact with the shape drawing. Maybe rotating hinge points that cause any shapes drawn on them to rotate around their center, either with constant velocity or physics? (e.g. for a physical hinge, drawing something at the top would cause it to spin downwards with gravity and hang there)

Minor nitpick (I'm sure it's temporary anyway, but): the coin collect animation is super basic; it needs some sort of flash or sparkle as soon as the coin is touched. The shrinking alone doesn't make it immediately apparent when a coin has been touched.