That level requires building a puzzle in a very specific way, and if puzzles were sorted by difficulty it would definitely be later in the game (instead, I usually put these optional levels in as soon as all the interactions needed to solve them are introduced). I can only advise you that one of the previous optional puzzles, "Backtracking revisited", was intended to show you a way to force 'the guy' to go to a square that doesn't contain a button.