Wow! Some in depth feedback from my jam twin :D
In order of feedback given:
1) The plan to fix this issue is to add an undo. I did try to avoid the dead end scenario in a few places, but in a game where you can not pull blocks it is hard to prevent players from ever ending up in that situation.
2) Yeah, the pistons are a pain. The movement feels weird, because there isn't actually any grid based movement in this. It is actually all physics based. No animations here.
3) Yes, couldn't agree more. When I am making puzzle games I always plan to do lots of tiny levels; putting lots of thought into teaching all the mechanics (see level 1) and then I get carried away and stuff like level 4 happens. 10 more levels coming for the post jam (level 4 will become level 13)
Thanks for the feeback. I agree with all of your points! Very glad you liked the game :D