OK I'll level with you - Crypto might be the weirdest trick I've ever developed. A demonstration of a remarkable skill, subliminal code-breaking, you test to see if your participant can unknowingly decode the jumbled letters on the back of the image cards by having them pick first four options and finally one single image that *might* be "the one".
You reveal that they have, in fact, found "the one", and in order to prove it you produce a metal decoder card, with holes that line up with the letters on the back of their chosen card revealing the message YOU WILL PICK ME. When you then line this decoder card up with the other cards in the set the message instead, impossibly, tells them to pick the item they did, freely, pick.
This version of Crypto has updated code cards with subtle changes that remove any guesswork from the method, rendering it more or less self-working. The decoder card is now 3D printed here in the shed, from a light, flexible plastic, robust and less than 1mm thick (a big improvement over the old aluminium decoder for performers) and the new updated code/image cards are printed on hardwearing plastic poker stock.
These items are made to order and hand-finished so will not ship immediately, please be patient - I am printing them as fast as I can and I have got a backlog at the moment.