This articles is about the form of Solitaire called "Pas de Deux" as implemented in the computer program PySol. It's named after the Ballet term pas de deux ("dance for two").
In PySol Pas de Deux is categorized as a "Montana" type game.
Pas du Deux is played with two decks which are kept separated. On is shuffled and laid out, all cards face up, in a tableau of four rows by thirteen columns (4x13). The other deck is shuffled and used as a talon (or stock).
One proceeds through the talon one card at a time. Whichever card appears next on the talon signifies the single card in the tableau which can be moved. That card can be moved horizontally or vertically ... swapping with any card along those axes. The player only gets one redeal. (In other words one only gets two passes through the talon).
The object of this game is to arrange all of the cards from ace to king (left to right) with clubs at the top, followed by spades, hearts and diamonds.
This is a surprisingly difficult game. It's relatively easy to get within three or four swaps of the winning position but almost impossible to win within the limited two passes through the talon.