Klondike

Klondike is the game almost everyone means by the word solitaire — the one bundled with Windows for decades, and the layout most people picture when they imagine cards fanned out in seven columns. It is a game of clearing your own way: the cards you need are usually face down underneath the cards you can see, and every move is a small decision about whether to dig or to bank.

That tension is what has kept it going. The rules take a minute to learn and the decisions take much longer to get good at, because the obvious move — sending an Ace to its foundation the moment it appears — is often the move that loses the game. Klondike is also not always winnable. Depending on the draw rule, a meaningful share of deals cannot be beaten no matter how well they are played, which is either the game's great flaw or the reason it stays interesting, depending on who you ask.

Deal seven columns, the first holding one card and the seventh holding seven, with only the top card of each face up. Build the columns downward in alternating colours — a red six onto a black seven — and move cards up to four foundation piles that each build a suit from Ace to King. Turning over a face-down card is what opens the layout up, so freeing them is most of the game. An emptied column can only be filled by a King, or by a run of cards headed by one. Cards you cannot place go through the stock, which you turn either one or three at a time depending on the variant you are playing.

Uncovering face-down cards beats advancing the foundations. A card sent to a foundation early is a card you can no longer build on, and Klondike deals routinely stall because an Ace or two went up before the columns were dug out. Prefer the move that flips a face-down card, and among several such moves prefer the one in the longest column, since that is where the most cards are trapped. Hold an empty column until you have a King worth putting there rather than filling it with the first one that appears. Wikipedia puts the odds of winning between roughly 18% and 43% depending on the draw rule and how well you play — with full knowledge of the deal, about 82% of games are theoretically winnable, so most losses are information problems rather than dead deals.