Pretty cool game, even if I'm not very good at precision platformers.
It would be nice if returning to a checkpoint also turns the time back. Otherwise, after 1 or 2 deaths, I restore at the checkpoint, but there's no way I can actually finish. There's also no option to quickly restart (you have to quit to the menu).
Also, on the second level, it seems like it's fairly random as to whether you get through the gap at the top after crouching.