Go is a strategic, two-player board game originating in ancient China between 2000 BC and 200 BC.

Go is a popular game in East Asia. The development of Internet play has served to increase its popularity notably throughout the rest of the world, in recent years. The English name Go originated from the Japanese character 碁 (go). The Chinese name 圍棋 w�iq� roughly translates to the "Board Game of Surrounding (One's Opponent)", or, less literally, the "Enclosing Game".

Philosophy

According to legend, the game was used as a teaching tool after an ancient Chinese Emperor designed it for his son, who he thought needed to learn discipline, concentration, and balance. The son went on to become the first great player, a good emperor, and a balanced human being. Another suggested genesis for the game states that in ancient times, Chinese warlords and generals would use pieces of stone to map out attacking positions. See also history of Go.

Go is deep, as playing against any stronger player will demonstrate (depth of the game as established by ELO ranking in Go). With each new level (rank) comes a deeper appreciation for the subtlety involved, and for the insight of stronger players. Beginners often start by randomly placing stones on the board, as if it were a game of chance — and they inevitably lose to experienced players. But soon an understanding of how stones connect to form strength develops, and shortly afterward a few basic common opening sequences may be understood. Learning the ways of life and death helps to develop one's situational judgement.

Further experience yields an understanding of the board, the importance of the edges, then the efficiency of developing (in the corners first, then walls, then center). Soon, the advanced beginner understands that territory and influence are somewhat interchangeable — but there needs to be a balance. Best is to develop more or less at the same pace as the opponent, in both territory and influence. This intricate struggle of power and control makes the game highly dynamic.

Rules

This picture shows one black chain and two white chains. Their respective liberties are shown with dots. Note that liberties can be shared between stones and chains. If white plays where its two chains share a liberty, the chains will be connected into one.

Basic rules

If white plays at A, the black chain loses its last liberty, and is captured and removed from the board.

• Two players, black and white, take turns placing a stone (game piece) on the points (intersections) of a 19 by 19 board (grid). Black moves first.
• Stones must have liberties (empty adjacent points) to remain on the board. Stones connected by lines are called chains, and share their liberties.
• When a stone or a chain of stones is surrounded by opponent stones, so that it has no more liberties, it is captured and removed from the board.
• "Ko rule": A stone cannot be played on a particular point, if doing so would recreate the board position after the same player's previous turn.
• A player may pass instead of placing a stone. Two consecutive passes end a game, beginning the scoring.
• A player's score is the number of empty points enclosed only by his stones plus the number of points occupied by his stones. The player with the higher score wins.

This is the essence of the game of Go. The possibility and threat to capture opposing stones provides strategic variation and makes the game interesting. (Also see strategy.)

For a more detailed treatment, see Go rules. Note in particular that there are other rulesets which count the score differently, yet almost always produce the same result.

Go allows to play not only even games (games between players of roughly equal strength) but also handicap games (games between players of unequal strength), see optional rules.

Game 5 of the 2002 LG Cup final between Choe Myeong-hun (white) and Lee Se-dol (black) at the end of the opening stage; white has developed large moyo (potential territory), while black has strong influence.

Optional rules

Optional Go rules might set the following among other aspects:

• compensation points ("komi") for the right to start alternate play
• compensation stones ("handicap") placed on the board before alternate play (this allows players of different strengths to play interesting games)
• thinking times

For details see Go rules. Also see Go rules of play and strategy.

Strategy

Basic strategic aspects include the following:

• Connection: Keeping one's own stones connected means that fewer groups need defense.
• Cut: Keeping opposing stones disconnected means that the opponent needs to defend more groups.
• Life: This is the ability of stones to avoid their removal. Usually life requires at least two "eyes" for a group of stones.
• Death: The absence of life, resulting in the removal of a group.

Also see details of Go strategy and tactics, Go rules of play, and optional rules.

Nature of the game

Although rules of Go can be written so that they are very simple, the game strategy is extremely complex. Go is a complete-knowledge, deterministic, strategy game: in the same class as chess, checkers (draughts), and reversi. Its depth arguably exceeds even those games. Its large board and lack of restrictions allows great scope in strategy. Decisions in one part of the board may be influenced by an apparently unrelated situation, in a distant part of the board. Plays made early in the game can shape the nature of conflict a hundred moves later.

The game emphasises the importance of balance on multiple levels, and has internal tensions. To secure an area of the board, it is good to play moves close together; but to cover the largest area one needs to spread out. To ensure one does not fall behind, expansionist play is required; but playing too broardly leaves weaknesses undefended that can be exploited. Playing too low (close to the edge) secures insufficient territory; yet playing too high (far from the edge) allows the opponent to invade. Many people find the game attractive for its reflection of polarities also found in life.

See Go strategy and tactics for an introductory explanation of how to play well, and the Go demonstration game.

It is commonly said that no game has ever been played twice. This may be true: On a 19�19 board, there are about 3³⁶¹�0.012 = 2.1�10¹⁷⁰ possible positions, most of which are the end result of about (120!)² = 4.5�10³⁹⁷ different (no-capture) games, for a total of about 9.3�10⁵⁶⁷ games. Allowing captures gives as many as

possible games (http://senseis.xmp.net/?NumberOfPossibleOutcomesOfAGame), most of which last for over 1.6�10⁴⁹ moves! (For two comparisons: the number of legal positions in chess is estimated to be between 10⁴³ and 10⁵⁰; and physicists estimate that there are not more than 10⁹⁰ protons in the entire visible universe.)

Computers and Go

Although attempts have been made to program computers to play Go, success in that area has been moderate at best - development in this area has not reached the level of Chess programs. Even the strongest programs are no better than an average club player, and would easily be beaten by a strong player even getting a nine-stone handicap. This is attributed to many qualities of the game, including the "optimising" nature of the victory condition, the virtually unlimited placement of each stone, the large board size, the nonlocal nature of the Ko rule, and the high degree of pattern recognition involved. For this reason, many in the field of artificial intelligence consider Go to be a better measure of a computer's capacity for thought than chess. See the article on Computer Go for details.

Use of computer networks to allow humans to meet, discuss games, and play one another, although generally considered inferior to face-to-face play, is becoming much more common. There are servers and software to facilitate this; see Additional Resources below for more information.

Other board games commonly compared with Go

Go appears to stand apart among games in its rules and gameplay; it is difficult to find another board game which could be considered of the same "family" as Go. However, on learning about the game, people will attempt to compare it with other games they may already have experienced. This is a list of some games that are played with similar equipment or come from the same area.

• Variations of chess
  • Western chess: This game dominates Western culture as the pinnacle of strategic game play; its history in the culture stretches back many centuries. By comparison, Go has only been known to Western culture as a challenging strategic game since the 1950s.
  • Shogi: Early Western literature often made the error of referring to Go as "Japanese Chess". The Japanese do have their own variant of Chess, called Shogi; it is much more similar to the other Chess variants than to Go. Shogi schools were founded in Japan about the same time as Go schools, but the game never received as much favour as Go.
  • Xiangqi: This is the Chinese variant of Chess, usually called "Chinese Chess" by Westerners. Like most Chess variants, it has great depth of strategy, but bears few similarities to Go in game play.
  • Janggi: This is the Korean variant of Chess, usually called "Korean Chess". It is also very different from Go in game play. Go and Janggi are the two main board games played in Korea, but Go is arguably more popular as there are professional Go players and Cable Television channels devoted to Go.
• Hex is a connection game which is often compared to go; though it can have some depth, its object is entirely different.
• Reversi: Marketed by Mattel as "Othello", Reversi bears superficial similarity to Go, with black and white circular pieces, an undifferentiated grid for a board, simple rules, and a goal of covering more of the board than the opponent. The game play is quite unlike Go, however, and the depth of strategy in Reversi is not comparable to Go.
• Gomoku, Renju and Pente: Played with the same equipment as Go (a 19x19 grid, black and white stones), in these games the goal is to create five stones in a row. The rules are thus completely unrelated, and the game style is much shorter and less strategic than Go.
• Alak is a Go-like game restricted to a single spatial dimension.

Traditional Go game equipment

After move 40 of round 1 of the 1989 Meijin tournament, little territory has been claimed.

Although one could play Go with a piece of card for a board and a bag of plastic tokens, Go players pride themselves on their game sets.

The traditional Go board (called a goban in Japanese) is solid wood, about 15-20cm thick, and stands on its own attached legs. They are preferably made from the rare golden-tinged Kaya tree (http://green-water.riken.go.jp/natural-e/Images/tree-watch/000630m/images/000630-35m.jpg) (Torreya nucifera (http://ag.udel.edu/udbg/conifers/descriptions/t_nucifera.html)), with the very best made from Kaya trees up to 700 years old.

Players sit on reed mats (tatami) on the floor to play. The stones (go-ishi) come in matching solid wood pots (go-ke) and are made out of clamshell (white) and slate (black) and are extremely smooth. The natural resources of Japan have been unable to keep up with the enormous demand for the native clams and slow-growing Kaya trees; both must be of sufficient age to grow to the desired size, and they are now extremely rare at the age and quality required, raising the price of such equipment tremendously.

In clubs and at tournaments, where large numbers of sets must be maintained (and usually purchased) by one organization, the expensive traditional sets are not usually used. For these situations, table boards (of the same design as floor boards, but only about 2-5cm thick and without legs) are used, and the stones are made of glass rather than slate and shell. Bowls will often be plastic if wooden bowls are not available. Plastic stones could be used, but are considered inferior to glass as they are generally much lighter, and most players find that not even the lower price justifies their unpleasantness.

The dimensions of the board (traditionally the grid is 45.45cm long and 42.42cm wide, with space beyond to allow stones to be played on the edges and corners of the grid) often surprise newcomers: it is not a perfect square, but is longer than it is wide, roughly in the proportion 12:11. Two reasons are frequently given for this. One is that when the players sit at the board, the angle at which they view the board gives a foreshortening of the grid; the board is slightly longer between the players to compensate for this. Another reason is that the Japanese aesthetic finds any structure which is perfectly symmetrical to be in bad taste, and the board is not made a perfect square for this reason.

Traditional stones are made so that black stones are slightly larger in diameter than white; this is probably to compensate for the optical illusion created by contrasting colors that makes the white stones appear larger on the board than black stones. The difference is slight, and since its effect is to make the stones appear the same size on the board, it can be surprising to discover they are not.

The bowls for the stones are of a simple shape, like a flattened sphere with a level underside. The lid is loose-fitting and is upturned before play to place opponent's stones captured during the game. The bowls are usually made of turned wood, although small lidded baskets of woven bamboo or reeds make an attractive cheaper alternative.

There is even an art to placing a Go stone, held between the tips of the outstretched index and middle fingers and striking the board firmly to create a sharp click. Many consider the acoustic properties of the wood of the board to be quite important. The traditional goban will usually have its underside carved with a pyramid called a Heso recessed into the board. Tradition holds that this is to give a better resonance to the stone's click, but the more conventional explanation is to allow the board to expand and contract without splitting the wood. A board is seen as more attractive when it is marked with slight dents from decades – or centuries – of stones striking the surface.

The Go world

Ranks

Three Japanese professional Go players observe some younger amateurs as they dissect a life and death problem in the corner of the board, at the US Go Congress in Houston, 2003.

See main article Go ranks and ratings

In countries where Go is popular, ranks are employed to indicate playing strength. From about the sixteenth century, the Japanese formalised the teaching and ranking of Go. The system is comparable to that of martial arts schools; and is considered to be derived ultimately from court ranks in China.

Beginning players today start at a rank of between 25 and 30 kyu. The kyu ranking then decreases in magnitude as the player becomes stronger, dropping down to 1 kyu or 1k. Since beginners will commonly progress through elementary concepts quickly, it may be difficult to set a solid kyu ranking for new players. Players who have progressed through the kyu ranks and passed the 1 kyu mark are then ranked at 1 dan or 1d, sometimes called shodan. The player then could advance through the amateur dan ranks up to amateur 7 dan, which only few players achieve. That playing level is roughly equivalent to where the ranks for professionals start with pro 1 dan going up to 9 dan (also sometimes called ping or p as in 9 p to avoid confusion between a 1 dan professional and a weaker amateur 6 dan). The distinction between each amateur rank is, by definition, one handicap stone. Professional ranks are awarded by professional organisations and though they are less well defined, they are closer, so that the difference between an average 1p and a prime 9p may be three handicap stones (however, tournament games are even).

In other words, the difference in rank between two players is theoretically equal to the number of handicap stones required for each player to have an even chance of winning. Beating this handicap consistently is the indicator that a player's strength has improved, and his rank should be adjusted upward by one stone, thus changing the number of handicap stones required.

Timing

Like many other games, a game of Go may be timed. There are three typical methods of timing a game:

• Absolute: a specific amount of time is given for the entire game, regardless of how fast or slow each player is.
• Byo-Yomi (Japanese Timing): a player has a certain number of time periods (typically around 30 seconds). After each move, the number of time periods that the player took (possibly zero) is subtracted. For example, if a player has three 30-second time periods and takes 30 or more (but less than 60) seconds to make a move, he loses one time period. With 60-89 seconds, he loses two time periods, and so on. If, however, he takes less than 30 seconds, the timer simply resets without subtracting any periods.
• Canadian Byo-Yomi: a player must make a certain number of moves within a certain period of time. For example, 5 moves within 2 minutes. If 5 moves are made in time, the timer resets to 2 minutes again. (The Origins of Canadian Byo-Yomi (http://pages.infinit.net/steven/byoyomi.htm))

Japanese Timing is equivalent to Canadian Byo-Yomi when the "certain number of moves" is equal to one.

Top players

Although the game was developed in China, in recent centuries the strongest players in the world have come from Japan. However, top players from China (since the 1980s) and South Korea (since the 1990s) have reached the same or an even higher level. Nowadays, top players from these three countries are of comparable strength, although top Korean players seem to have an edge, dominating the major international titles. All three countries have a number of professional Go tournaments. The top Japanese tournaments have a prize purse comparable to that of professional golf tournaments in the United States. Tournaments in China and Korea are less lavishly funded.

Players from other countries have traditionally been much weaker, except for some players who have taken up professional courses in one of the Asian countries. This is attributable to the fact that details of the game have been unknown outside of Asia for most of the game's history. A German scientist, Otto Korschelt, is credited with the first systematic description of the game in a Western language in AD 1880; it was not until the 1950s that Western players would take up the game as more than a passing interest. In 1978, Manfred Wimmer became the first Westerner to receive a professional player's certificate from an Asian professional Go association. It was not until 2000 that a Westerner, Michael Redmond, achieved the top rank awarded by an Asian go association.

See also: Go players

History

See main article history of Go

The origins of the game are unknown, but the oldest surviving references come from China in the 6th century BC. Except for changes in the board size and starting position, Go has essentially kept the same rules since that time, which quite likely makes it the oldest board game still played today. It had reached Japan by the 7th century, and gained popularity at the imperial court in the 8th. By the beginning of the 13th century, the game was played in the general public in Japan.

Early in the 17th century, the then best player in Japan, Honinbo Sansa, was made head of a newly founded Go academy (the Honinbo school, the first of several competing schools founded about the same time), which developed the level of playing greatly, and introduced the martial-arts style system of ranking players. The government discontinued its support for the Go academies in 1868 as a result of the fall of the Tokugawa shogunate.

In honour of the Honinbo school, whose players consistently dominated the other schools during their history, one of the most prestigious Japanese Go championships is called the "Honinbo" tournament.

Historically, Go has been unequal in terms of gender. However, the opening of new, open tournaments and the rise of strong female players, most notably Rui Naiwei, has in recent years legitimised the strength and competitiveness of emerging female players.

Around 2000, in Japan, the manga (Japanese comic) and anime series Hikaru no Go has popularized Go among the youth and started a Go boom in Japan. In January 2004, the Hikaru no Go manga also began running in the American periodical Shonen Jump. Whether this will lead to a strong following in the US is yet to be seen.

Mathematical theory of Go endgames

Elwyn Berlekamp and David Wolfe have developed a mathematical theory of the late endgame in Go based on the combinatorial game theory of John Horton Conway. It is outlined in their book, Mathematical Go (ISBN 1568810326). Whilst not of general utility in most play, it greatly aids the analysis of certain classes of positions.

It is worth noting that John Conway developed the mathematical concept of Surreal numbers while studying Go endgames.

Go in popular culture

Go has been mentioned in many novels and short stories published in the Orient, and occasionally turns up in Western media as well. The game of Go plays a part in the American TV miniseries, Wild Palms which references a piece of computer technology called a "Go chip." The game also appeared, unexpectedly, in an episode of Star Trek: Enterprise entitled "The Cogenitor" in which it was revealed that Charles Tucker plays the game.

"Hikaru no Go" was a manga and anime series, in which a boy is taught to play Go by the spirit of an ancient Go player.

In 1951, Nobel Prize-winning author Yasunari Kawabata published The Master of Go, a novel based upon an epic game that took place over the course of several months in 1938. An English translation appeared in 1972, around the time of Kawabata's death.

See also

• Computer Go
• Games played with Go equipment
• Go concepts
• Go handicap
• Go players
• Go proverb
• Go rules
• Go strategy and tactics
• List of free Go programs
• List of Go topics
• Nihon Ki-in

External links

Learning Go

• The Interactive Way To Go (http://playgo.to/interactive/) is an excellent resource to learn the basics; includes Java applets.
• British Go Association's introduction to Go (http://www.britgo.org/intro/intro2.html)
• The Rules of Go (http://www.toycrossing.com/go/index.shtml)
• How To Play Go (http://unkx80.netfirms.com/weiqi/howtoplaygo/)
• Samarkand (http://www.samarkand.net/Academy/learn_go/overview.html) is owned by Janice Kim 3p and has a very good beginner introduction.
• goproblems.com (http://www.goproblems.com/) has over 3000 problems for practice in a Java applet.
• GoBase (http://gobase.org/studying/problems/academy/) has a collection of 750 problems used in Korea to help develop players of amateur dan strength.

Resources

• Sensei's Library (http://senseis.xmp.net/) is a wiki devoted entirely to the game of Go - it even has special markup for displaying Go diagrams.
• The Usenet newsgroup rec.games.go (news:rec.games.go) has its own FAQ document, the rec.games.go FAQ (http://www.faqs.org/faqs/games/go-faq/).
• SIMPLEKO (http://www.simpleko.com.ar/) offer go tables & go boards to play the Game.

Go history

• History of Go in ancient China, Korea and Japan (http://gobase.org/history/)

Go organisations

• American Go Association (http://www.usgo.org)
• Asociacion Argentina de Go (http://www.go.org.ar/)
• Belgian Go Federation (http://www.gofed.be/)
• British Go Association (http://www.britgo.org/)
• Canadian Go Association (http://www.go-canada.org)
• China Go Association (http://www.weiqi.cc/)
• Deutscher Go-Bund (http://www.dgob.de/index.htm?home.php)
• Dutch Go Association (the Netherlands) (http://www.gobond.nl/)
• European Go Federation (http://www.european-go.org/www/wmembers.htm)
• French Go Association (http://ffg.jeudego.org/intro-e.html)
• Italian Go Association (http://www.figg.org)
• Japan Go Association (http://www.nihonkiin.or.jp/index-e.htm)
• Korea Baduk Association (http://www.baduk.or.kr)
• South African Go Association (http://www.sa-go.co.za)
• Singapore Weiqi Association (http://weiqi.org.sg/)
• Swedish Go Association (http://www.gosverige.com/)
• Taiwan Chi Yuan (http://taiwango.org.tw/)
• International Go Federation (http://www.nihonkiin.or.jp/igf/)

Internet Go

Go can be played on the Internet against opponents from around the world on numerous Go servers (http://www.britgo.org/gopcres/play.html#server):

• The Kiseido Go Server (http://www.kiseido.com/) is such a server, complete with its own easy-to-use Java client, teaching facilities and introductory material.
• The Internet Go Server (http://www.pandanet.co.jp/English/), the "original" server. Several official and 3rd party clients are available.
• The No Name Go Server (http://nngs.cosmic.org/), similar to the IGS, but with a smaller community.
• The Legend Go Server (http://www.lgs.taiwango.net/), located in Taiwan, with its own English client.
• The Dash Go Server (http://english.dashn.com/), Korean server with an English Windows client.
• The Tygem Go (http://www.tygem.com/), located in Korea, with its own client.
• The Oro Go (http://www.orozone.com/), located in Korea, with its own client.
• The Dragon Go Server (http://www.dragongoserver.net/), a turn-based server run on open source software.
• The LittleGolem (http://www.littlegolem.net/), another turn-based server, this one centred around tournament play.
• The Playray Go (http://www.playray.com/play/go/), quite a new browser based Go server, includes many options and a ranking system of its own. Players from various countries.

Recorded games

• The popular SGF file format (http://www.red-bean.com/sgf/) is used to exchange Go lessons and recorded games.
• Fuseki.Info (http://fuseki.info) - Online professional Go games database (more than 35000 games). Contains game records, game lists, fuseki and joseki trees. More than 3000 games for free.
• Several free reading and authoring programs are listed at Gobase's SGF editors list (http://gobase.org/sgfeditors.html)
• gobase.org also hosts a database of more than 30000 professional Go games in SGF format (free registration required, which takes 1-2 days to process)
• My Friday Night Files (http://www.xs4all.nl/~rongen17/) provides more than 2000 professional games, including almost all known games of Cho Chikun
• A smaller collection of professional games in SGF format is available without registration at Andries E. Brouwer's Go Games (http://homepages.cwi.nl/~aeb/go/games/).
• Amateur games are reviewed at The Go Teaching Ladder (http://gtl.jeudego.org/).

Go software

• GNU Go (http://www.gnu.org/software/gnugo/gnugo.html), free Go-playing engine
• gGo (http://panda-igs.joyjoy.net/java/gGo/), SGF editor and client for IGS, in Java; and native variants, qGo (http://qgo.sourceforge.net) and glGo (http://www.pandanet.co.jp/English/glgo/) (has a 3D display)
• CGoban1 (http://cgoban1.sourceforge.net), Go client (Linux, etc)
• CGoban2 (http://kgs.kiseido.com/), Go client for KGS in Java. Also functions as an SGF editor.
• Goban (http://www.sente.ch/software/goban/), standalone (against GNU Go) and Internet Go client for Mac OS X
• HandyGo (http://handygo.sourceforge.net/index.htm), J2ME Go client that runs on java-enabled cellphones and PDAs.
• BiGo Assistant (http://bigo.ufgo.org/) - BiGo Assistant is Go (Baduk, Weiqi) games (professional and amateur) database software. It allows searching by fuseki, joseki, positions and game information fields.
• WikiTeX Go (http://wikisophia.org/wiki/Wikitex#Go) supports SGF for inserting go directly into Wiki articles.
• PilotGOne (http://minas.ithil.org/pilotgone/) A Go game recorder and SGF viewer/editor for PalmOS.
• Hikarunix (http://www.hikarunix.org), a Linux live CD dedicated to studying and playing Go.
• Godot (http://jenslieberum.de/index.html), a java applet that plays Go.