Touch Arcade: Back in the fourteenth century, a hot new device hit Europe: it was pocket-sized, and people used it for entertainment as well as divination, and in order to make poor financial decisions. Playing cards were hot (and expensive) and it was amazing all the things you could do with them. The more things change, the more they stay the same. Reiner Knizia: Card Buster [$0.99] is optimized for iOS, but it will also run on a deck of playing cards, if you still have them.
