also, just press the question mark, for some reason it gives the solution (maybe it could be made to make some pieces unmovable, so you know what you need for it and what not, but giving the solution is a bold move)
no i did not use it to solve 37, i was looking at 39 and couldn't find it, so i wanted a small hint to know if i was doing it right, i was close to the solution at least, im not ganne use it elsewhere, as the full solution kinda ruins the gimmick