Thank you for playing! I will for sure add as speed-up button, the critters ended up going quite slowly in the end.
You are totally allowed to reset the critters back to the start even after unlocking obstacles, I wanted the game to be solvable both the “easy way” and the hard way of placing everything at once. If I had more time, I was planning on adding a “star” system to the levels, where you would get a golden star on the level if you completed it without resetting the critters.