Card Trick at Anamorph
Five cards, one glowing

A Card Trick

This is the explanation of a pretty neat card trick you can do for friends over the Web. In order to do the trick, you'll need five things: The effect of the trick is as follows: the magician opens this Web page (or a second, similar page that doesn't contain this explanation), but doesn't touch the computer for the duration of the trick. The spectator is given a deck of cards, and asked to choose any five cards; these cards can be chosen at random, or the spectator can choose five cards he wants to use.

The magician takes one of the five cards out of the set, and asks his friend to enter the other four cards into a form on the Web page (a working version can be found below). The Guess button is pressed, and a picture of the fifth card is displayed.

In this document, I explain everything about the trick except for its secret. But hints are given to figure out how the trick is done, and you can always ask me to tell you.

The remainder of this document contains:

The Trick Itself

If you know how the trick is done, and are going to show the trick to friends, you're probably better off going to the page that contains only the trick, without this explanation. If you don't know how the trick is done, you can practice it from here, but you'll need to read the rest of the document as well.

Enter the first card: of

And the second card: of

Now the third card: of

And finally the fourth card: of


A Warning

If you stumbled across this page accidently, and started choosing cards and pressing buttons above, you're probably saying "huh?"

This trick is most mystifying when it is demonstrated by someone who knows how it's done. If you don't know the trick's secret, using the mechanism above might confuse you. But hints on how the trick is done are given below.

How It Works

Sorry. I can't just give the secret away that easily, can I? I want people to be able to do this trick, but if everyone in the world knows how to do it, it won't be as effective. However, there are at least four ways you can find out how the trick is done:

  1. Treat this like a puzzle. Experiment with the form above. Why is it that the cards Ace of Diamonds, Four of Clubs, King of Hearts, and Nine of Hearts yield the fifth card Six of Clubs? Why do any four cards generate any particular fifth card? Try different combinations of cards and see what you get.

  2. Ask me questions. If you're trying to figure out how to do the trick, and you ask me relevant questions, I'll answer them. Yes or no questions only, please.

  3. Read the code. A version of this card trick that runs the old-fashioned way (off of your own computer) is available. If you've got a Macintosh (with HyperCard), and you know how to program, you can try to figure it out by reading the code.

  4. Get me to tell you. Well, there's not much of a chance of this happening. Since I put up this page in May 1995, two or three people per week have written to me, asking questions. I've only told the secret once; it bothered me a bit, and I haven't done it since then. But... there is a big hint that I can give if you get stuck. Write to me and tell me what you figured out about the trick; if you've figured out the two small things, I'll give you a good hint for the one big thing.

History of this Card Trick

This trick was originally posted as a puzzle in the rec.puzzles newsgroup. Someone in the newsgroup had been applying for a programming job, and as part of the interview, they gave him half an hour to figure out how this trick might be done. He didn't have to solve the puzzle to be hired, but progress on it would have helped him. (I don't remember whether or not he got the job).

I tried to solve the puzzle, and came close, but my solution wasn't perfect. A few different solutions were posted, the most elegant being by Bob Vesterman (does anyone know where to reach him?). I implemented Bob's solution in HyperCard, and later adapted it for the Web.

Discussion

I'd like to implement other tricks that can be done over the Web. If you know of any other good tricks, or have comments or questions about this one, please let me know.

References

Card Trick at Anamorph
Last Updated: August 15, 2002. Created April 2, 1995
Copyright 1995 Robert Orenstein. Your Comments are welcome: atempaddress@netscape.net