Just when you thought jigsaw puzzles couldn't get any more befuddling, along comes the Invisi-Puzzle! This infuriating puzzle is made up entirely of transparent perspex pieces and is guaranteed to push your patience to the absolute brink. Sure you can slot together a few edge pieces, even casual puzzlers can do that, but just you wait 'til you're faced with a box full of almost identical shapes - and not even a reference picture to help you out. Thankfully there are 'only' 300 pieces, but your dining table is going to be out of action for months!