Go, weiqi, or baduk is an abstract strategy board game for two players in which the aim is to fence off more territory than the opponent. The game was invented in China more than 2,500 years ago and is believed to be the oldest board game continuously played to the present day. A 2016 survey by the International Go Federation's 75 member nations found that there are over 46 million people worldwide who know how to play Go, and over 20 million current players, the majority of whom live in East Asia.
The playing pieces are called stones. One player uses the white stones and the other black stones. The players take turns placing their stones on the vacant intersections (points) on the board. Once placed, stones may not be moved, but captured stones are immediately removed from the board. A single stone (or connected group of stones) is captured when surrounded by the opponent's stones on all orthogonally adjacent points. The game proceeds until neither player wishes to make another move.
When a game concludes, the winner is determined by counting each player's surrounded territory along with captured stones and komi (points added to the score of the player with the white stones as compensation for playing second). Games may also end by resignation.
The standard Go board has a 19×19 grid of lines, containing 361 points. Beginners often play on smaller 9×9 or 13×13 boards, and archaeological evidence shows that the game was played in earlier centuries on a board with a 17×17 grid. The 19×19 board had become standard by the time the game reached Korea in the 5th century CE and Japan in the 7th century CE.
Go was considered one of the four essential arts of the cultured aristocratic Chinese scholars in antiquity. The earliest written reference to the game is generally recognized as the historical annal Zuo Zhuan ( BCE).
Despite its relatively simple rules, Go is extremely complex. Compared to chess, Go has a larger board with more scope for play, longer games, and, on average, many more alternatives to consider per move. The number of legal board positions in Go has been calculated to be approximately , which is far greater than the number of atoms in the observable universe, which is estimated to be on the order of 1080.
Names of the game The name Go is a short form of the Japanese word (; ), which derives from earlier (), in turn from Middle Chinese (, Mandarin: , ). In English, the name Go when used for the game is often capitalized to differentiate it from the common word go. In events sponsored by the Ing Chang-ki Foundation, it is spelled goe.See, e.g.,
The Korean name () is a native derived term, most likely originally consisting of (Yale: , 'cultivated field') + (Yale: twǒlk, "stone", presumed dialectal variant of Seoul , 'stone'). Less plausible etymologies include a derivation of , referring to the playing pieces of the game, or a derivation from Chinese (), meaning 'to arrange pieces'.
Overview
Go is an adversarial game between two players with the objective of capturing territory: that is, occupying and surrounding a larger total empty area of the board with one's stones than the opponent. As the game progresses, the players place stones on the board, creating stone "formations" and enclosing spaces. Once placed, stones are never moved on the board, but when "captured" are removed from the board. Stones are linked together into formations by being adjacent along the black lines, not on diagonals (of which there are none). Contests between opposing formations are often extremely complex and may result in the expansion, reduction, or wholesale capture and loss of formations and their enclosed empty spaces (or "eyes"). One essential aspect of the game is control of the sente (that is, controlling the offense, so that one's opponent is forced into defensive moves); this usually changes several times during play.
Initially, the board is bare. Players take turns, placing one stone per turn. As the game proceeds, players try to link their stones together into "living" formations (meaning that they are permanently safe from capture), while threatening to capture their opponent's stones and formations. Thus, stones have both offensive and defensive characteristics, depending on the situation.
An essential aspect of the game is that any formation of stones needs to have, or be capable of making, at least two enclosed open points known as eyes, in order to preserve itself from being captured. A formation having two or more eyes cannot be captured, even after it is surrounded by the opponent on the outside, because each eye constitutes a liberty that must be filled by the opponent as the final step in capture. Once surrounded, a formation with a single eye can be captured on the next move, by one's opponent filling the eye and completely surrounding all stones in the formation; however, with two eyes, completely surrounding the formation is impossible, as filling one eye does not capture the formation, and instead would simply sacrifice the stone filling that eye. Thus, a formation having two or more eyes is said to be unconditionally alive, meaning that it can never be captured, while a group that cannot form two eyes is said to be dead and can be captured unless it is subsequently connected to a formation with a second eye.
The general strategy is to place stones to fence-off territory, attack the opponent's weak groups (trying to kill them so they will be removed), and always stay mindful of the life status of one's own groups. Situations where mutually opposing groups must capture each other or die are called capturing races, or semeai. In a capturing race, the group with more liberties will ultimately be able to capture the opponent's stones. Capturing races and the elements of life or death are the primary challenges of Go.
In the end game, players may pass rather than place a stone if they think there are no further opportunities for profitable play. The game ends when both players pass or when one player resigns. In general, to score the game, each player counts the number of unoccupied points surrounded by their stones and then subtracts the number of stones that were captured by the opponent. The player with the greater score (after adjusting for handicapping called komi) wins the game.
In the opening stages of the game, players typically establish groups of stones (or bases) near the corners and around the sides of the board, usually starting on the third or fourth line in from the board edge rather than at the very edge of the board. The edges and corners make it easier to develop groups which have better options for life (self-viability for a group of stones that prevents capture) and establish formations for potential territory. Players usually start near the corners, because establishing territory is easier with the aid of two edges of the board. Established corner opening sequences are called joseki and are often studied independently. However, in the mid-game, stone groups must also reach in towards the large central area of the board to capture more territory.
Dame are points that lie in between the boundary walls of black and white, and as such are considered to be of no value to either side. Seki are mutually alive pairs of white and black groups where neither has two eyes.
Ko (Chinese and Japanese: ) is a potentially indefinitely repeated stone-capture position. The rules do not allow a board position to be repeated. Therefore, any move which would restore the previous board position would not be allowed, and the next player would be forced to play somewhere else. If the play requires a strategic response by the first player, further changing the board, then the second player could "retake the ko," and the first player would be in the same situation of needing to change the board before trying to take the ko back. And so on. Some of these ko fights may be important and decide the life of a large group, while others may be worth just one or two points. Some ko fights are referred to as picnic kos when only one side has a lot to lose. In Japanese, it is called a hanami ko.
Playing with others usually requires a knowledge of each player's strength, indicated by the player's rank (increasing from 30 kyu to 1 kyu, then 1 dan to 7 dan, then 1 dan pro to 9 dan pro). A difference in rank may be compensated by a handicap—e.g., Black may be allowed to place two or more stones on the board to compensate for White's greater strength. There are different rulesets (Korean, Japanese, Chinese, AGA, etc.), which are almost entirely equivalent, except for certain special-case positions and the method of scoring at the end.
Basic concepts
Basic strategic aspects include the following: Connection: Keeping one's own stones connected means that fewer groups need to make living shapes, and the player has fewer groups to defend. Cut: Keeping opposing stones disconnected means that the opponent needs to defend and make living shape for more groups. Stay alive: The simplest way to stay alive is to establish a foothold in the corner or along one of the sides. At a minimum, a group must have two eyes (separate open points) to be alive. An opponent cannot fill in either of two (or more) eyes in their opponent's formation, as any such move is suicidal: suicidal plays are prohibited. Mutual life (seki) is better than dying: A situation in which neither player can play on a particular point without then allowing the other player to play at another point to capture. The most common example is that of adjacent groups that share their last few liberties—if either player plays in the shared liberties, they can reduce their own group to a single liberty (putting themselves in atari), allowing their opponent to capture it on the next move. Death: A group that lacks living shape is eventually removed from the board as captured. Invasion: Establishing a new living formation in an area where one's opponent had dominance reduces one's opponent's score in proportion to the area one occupies. Reduction: Placing a stone far enough into the opponent's area of influence to reduce the amount of territory they eventually get, but not so far that it can be cut off from friendly stones outside. Sente: A play that forces one's opponent to respond (gote). A player who can regularly play sente has the initiative and can control the flow of the game. Sacrifice: Allowing a group to die in order to carry out a play, or plan, in a more important area.
The strategy involved can become very abstract and complex. High-level players spend years improving their understanding of strategy, and a novice may play many hundreds of games against opponents before being able to win regularly.
One fundamental strategy, and learning technique, is to play one's stones in the position that one's opponent would wish to play their stone. Relatedly, switching positions (white changing to play black, and vice versa) is a useful way to learn how to see one's opponent's opportunities and strategy.
Strategy
Strategy deals with global influence, the interaction between distant stones, keeping the whole board in mind during local fights, and other issues that involve the overall game. It is therefore possible to allow a tactical loss when it confers a strategic advantage.
Novices often start by randomly placing stones on the board, as if it were a game of chance. An understanding of how stones connect for greater power develops, and then a few basic common opening sequences may be understood. Learning the ways of life and death helps in a fundamental way to develop one's strategic understanding of weak groups. A player who both plays aggressively and can handle adversity is said to display kiai, or fighting spirit, in the game.
Opening strategy