Card game

A card game is any game that uses cards as the primary device with which the game is played, whether the cards are of a traditional design or specifically created for the game (proprietary). Countless card games exist, including families of related games (such as poker). A small number of card games played with traditional decks have formally standardized rules with international tournaments being held, but most are folk games whose rules may vary by region, culture, location or from circle to circle.

Traditional card games are played with a deck or pack of playing cards which are identical in size and shape. Each card has two sides, the face and the back. Normally the backs of the cards are indistinguishable. The faces of the cards may all be unique, or there can be duplicates. The composition of a deck is known to each player. In some cases several decks are shuffled together to form a single pack or shoe. Modern card games usually have bespoke decks, often with a vast amount of cards, and can include number or action cards. This type of game is colloquially regarded as part of the broader "board game" hobby.

Games using playing cards exploit the fact that cards are individually identifiable from one side only, so that each player knows only the cards they hold and not those held by anyone else. For this reason card games are often characterized as games of "imperfect information"—as distinct from games of perfect information, where the current position is fully visible to all players throughout the game. Many games that are not generally placed in the family of card games do in fact use cards for some aspect of their play.

Some games that are placed in the card game genre involve a board. The distinction is that the play in a card game chiefly depends on the use of the cards by players (the board is a guide for scorekeeping or for card placement), while board games (the principal non-card game genre to use cards) generally focus on the players' positions on the board, and use the cards for some secondary purpose.

Playing cards were likely invented during the Tang dynasty around the 9th century due to the technological impact of woodblock printing. A 9th century text known as the Collection of Miscellanea at Duyang (Chinese: 杜阳杂编; pinyin: Dùyáng zábiān) by Tang writer Su E references a leaf game that has been cited as a card game. However it is uncertain if it was actually a card game.

The reference describes Princess Tongchang, daughter of Emperor Yizong of Tang, playing the "leaf game" in 868 with her husband's family. The first known book on the "leaf" game was called the Yezi Gexi and allegedly written by a Tang woman. It received commentary by writers of subsequent dynasties. The Song dynasty (960–1279) scholar Ouyang Xiu (1007–1072) asserts that the "leaf" game existed at least since the mid-Tang dynasty and associated its invention with the development of printed sheets as a writing medium. However, Ouyang also claims that the "leaves" were pages of a book used in a board game played with dice, and that the rules of the game were lost by 1067.

The earliest dated instance of a game involving cards occurred on 17 July 1294 when the Yuan dynasty Department of Punishments caught two gamblers, Yan Sengzhu and Zheng Zhugou, playing with paper cards. Wood blocks for printing the cards were impounded, together with nine of the actual cards. No description of the card game being played was provided.

Other games revolving around alcoholic drinking involved using playing cards of a sort from the Tang dynasty onward. However, these cards did not contain suits or numbers. Instead, they were printed with instructions or forfeits for whoever drew them. A playing card for a wine drinking game dating to the Yuan period (1271-1368) reads: