Welcome to Beleaguered Castle!
About
Technically, solitaire is an entire genre of single player games. The most common form of card solitaire is Klondike. Beleaguered Castle is solitaire, but it's not Klondike.
Rules
The rules for Beleaguered Castle are relatively simple. The Aces start play alone on the four foundations in the center of the play area. The remaining cards are dealt out face up in stacks of six to the eight tableaus. The goal is to build up each suit from the Ace to the King on the four foundations. Only a card that is of the same suit and that is next in sequence may be played on a foundation. Cards may also be moved from the top of any tableau onto another tableau if the moving card is one down in sequence from the card it is being moved onto, regardless of suit.