Plus many of the puzzles iterate on previous puzzles. You'll solve a puzzle, then find that the next one is almost the same but has one tiny difference that com

Plus many of the puzzles iterate on previous puzzles. You'll solve a puzzle, then find that the next one is almost the same but has one tiny difference that completely closes the door on your previous solution without opening any obvious new ones. These are great, because it often makes the second puzzle look completely impossible on first glance.