Nevermind, all I needed was a pen and paper! Damn trickery...even on a Monday when I work at half speed!
Here's the link to the card one. It's a little different but they both test your attentiveness. www.caveofmagic.com/pickcrd2.htm
yeaa they are fun...and i wont tell how it works, just because its entertaining to others, but if you think about it, its quite simple