Go (traditional Chinese: 圍棋; simplified Chinese: 围棋; pinyin: About this sound wéiqí; Japanese: 囲碁; rōmaji: igo[nb 2]; Korean: 바둑; romaja: baduk[nb 3]; literally: "encircling game") is an abstract strategy board game for two players, in which the aim is to surround more territory than the opponent.
The game was invented in ancient China more than 2,500 years ago, and is thus the oldest board game continuously played today. It was considered one of the four essential arts of the cultured aristocratic Chinese scholar caste in antiquity. The earliest written reference to the game is generally recognized as the historical annal Zuo Zhuan (c. 4th century BCE).
Despite its relatively simple rules, Go is very complex, even more so than chess, and possesses more possibilities than the total number of atoms in the visible universe. Compared to chess, Go has both a larger board with more scope for play and longer games, and, on average, many more alternatives to consider per move.
The playing pieces are called stones. One player uses the white stones and the other, black. The players take turns placing the stones on the vacant intersections (named "points") of a board with a 19×19 grid of lines. Beginners often play on smaller 9×9 and 13×13 boards, and archaeological evidence shows that the game was once played on a 17×17 grid. However, boards with a 19×19 grid had become standard by the time the game had reached what was then the Imperial Chinese Tributary State of Korea in the 5th century CE and later to what was then the Imperial Chinese Tributary State of Japan in the 7th century CE.
The objective of go—as the translation of its name implies—is to fully surround a larger total area of the board than the opponent.
Once placed on the board, stones may not be moved, but stones are removed from the board when "captured". Capture happens when a stone or group of stones is surrounded by opposing stones on all orthogonally-adjacent points. The game proceeds until neither player wishes to make another move; the game has no set ending conditions beyond this. When a game concludes, the territory is counted along with captured stones and komi (points added to the score of the player with the white stones as compensation for playing second) to determine the winner. Games may also be terminated by resignation.
As of mid-2008, there were well over 40 million Go players worldwide, the overwhelming majority of them living in East Asia. As of December 2015, the International Go Federation has a total of 75 member countries and four Association Membership organizations in multiple countries.