Double Solitaire / Simultaneous Solitaire
This is a competitive version of Klondike patience (solitaire). Each player plays with their own 52-card pack. The backs of the cards should if possible be different so that they can be sorted out after the game.
Each player deals a layout as for Klondike: 28 cards in 7 piles, each having the top card face up and the rest face down. The left hand pile has just one card, the second two, and so on, the right hand pile having seven cards. Between the players' layouts is space for the foundation piles, four piles per player, which can be played on by any player. Each player begins with a stack of 24 face-down cards.
There are two different ways this game can be played: the players may take turns, or it can be played as a race, with everyone playing simultaneously.
The turn based game is normally played as a two-player games, known as Double Solitaire. The player with the lower card on their one-pile starts - or in case of a tie whoever has the lower card on their two-pile and so on.
At your turn you can make a series of moves as in Klondike. You may move cards around on your own layout, move cards onto the foundation piles when they fit, and move cards from your discard pile to your layout or the foundations. You are not allowed to play onto or use your opponent's layout or discard pile. You end your turn when you cannot or choose not to make any other moves by turning over the top card of your face-down stack, and placing it on your face-up discard pile. Your opponent then plays.
The game ends when one player has played all the cards to the foundation piles and wins, or when both players are blocked, in which case the winner is the player who has played more cards to the foundation piles.
This game is possible with up to 6 or 7 or even more players, each beginning with their own pack of 52 cards. The moves in this version are the same as above, but the players do not take turns. All play at once, as fast as possible, but each using only one hand. When you cannot or do not wish to make further moves with your face up cards, you turn over the top three cards of your stack, put them face up on your discard pile and continue playing. If there are no more cards in your stack, you may turn your whole discard pile over to make a new stack, and turn over its top three cards to start a new discard pile.
Play continues until one player has played all their cards to the foundation piles and wins, or until all players are blocked, in which case the winner is the player who has played most cards to the foundation piles, or equivalently, the player who has fewest cards in their stack plus layout.
With more than two players, after one player has gone out, the game can be continued for 2nd place, 3rd place and so on. When the game blocks the remaining players are placed according to how many unplayed cards they have in their stack plus layout, the fewer the better.
In the two-player game, some play that if both players are blocked and have fewer than 7 cards in their stacks, they may agree each to turn all the cards of their stacks face up in a row and use any of the cards from their own stacks to make any further moves that are possible.
Software and Online Games
At Solitaire.com you can play two-player Simultaneous Solitaire against a computer opponent.