CardTrack is a tool which finds a selected card within a shuffled deck.

* Input the initial order of a deck of cards into CardTrack.
* Have a spectator give the deck a riffle or faro shuffle.
* Have a card selected and replaced into the deck.
* The cards can then be given one or two more riffle/faro shuffles, as well as a brief overhand shuffle.
* CardTrack's algorithms will then attempt to determine which card was selected.

To input the cards into CardTrack, the deck could be switched out and given to an accomplice. You could even perform the effect by mailing the deck to a spectator and having them send it back after following the instructions.

CardTrack works perfectly in conjunction with Martin Eisele's Vision app which will detect the order of the deck using the camera.

Note:
* CardTrack does its best to locate the selected card but may not always be accurate. This depends on the number of shuffles as well as the position of the replaced card. In testing, CardTrack works well with 2-3 riffle shuffles, but has also worked with 4 riffle shuffles + 1 overhand shuffle.
* This app is for entertainment purposes only.