Go variants
There are many variations of the simple rules of Go. Some are ancient digressions, while other are modern deviations. They are often side events at tournaments, for example, the U.S. Go Congress holds a "Crazy Go" event every year.
National variants
The difficulty in defining the rules of Go has led to the creation of many subtly different rulesets. They vary in areas like scoring method, ko, suicide, handicap placement, and how neutral points are dealt with at the end. These differences are usually small enough to maintain the character and strategy of the game, and are typically not considered variants. Different rulesets are explained in Rules of Go.In some of the examples below, the effects of rule differences on actual play are minor, but the tactical consequences are substantial.
Tibetan Go
Tibetan Go is played on a 17×17 board, and starts with six stones from each color placed on the third line. White makes the first move. There is a unique ko rule: a stone may not be played at an intersection where the opponent has just removed a stone. This ko rule is so different from other major rulesets that it alone significantly changes the character of the game. For instance, snapbacks must be delayed by at least one move, allowing an opponent the chance to create life. Finally, a player who occupies or surrounds all four corner points receives a bonus of 40 points, plus another 10 if the player also controls the center point.Sunjang baduk
Sunjang baduk is a different form of Go that evolved in Korea, which dates to the 16th century. Its most distinctive feature is the prescribed opening. The starting position dictates the placement of 16 stones as shown, and the first move is prescribed for Black at the center of the board. At the end of the game, stones inside friendly territory, which are irrelevant to boundary definition, are removed before counting territory.Classical Chinese go was played with the diagonal placement of two black stones and two white stones on the four star points in the corners. It is likely that Koreans played go in this form until it developed into Sunjang baduk in the 16th century.
It became antiquated in the early 20th century when it was largely replaced by modern go due to Japanese influence. There are around 45 surviving game records of Sunjang baduk, mostly from the 1880s. The last official game record was published in the Chosun Ilbo newspaper in March 1937. The game is between No Sa-ch'o and Ch'ae Keuk-mun.
In the early 20th century, the top ten strongest players ranged from about 4 dan amateur to 2 dan professional in terms of strength. From 1910 to 1945, Korea was a Japanese colony. The similarity between Sunjang Baduk and modern go as well as Japanese influence encouraged players to switch to the modern game. The strength and fame of visiting Japanese professional go players encouraged Koreans to abandon Sunjang baduk. This was supported by the father of modern Korean go, Cho Nam-ch'eol, who established close links to Japan by studying go there.
Bangneki
In another Korean variant, bangneki, the players wager on the outcome of the game. A fixed stake is paid for every ten points on the board by which the loser is beaten.Batoo
is a modern Korean variant. The name stems from a combination of the Korean words baduk and juntoo. It is played entirely in cyberspace, and differs from standard Go in a number of ways, most noticeably in the way in which certain areas of the board are worth different points values. The other principal difference is that both players place three stones before the game begins, and may also place a special "hidden stone", which affects the board as a regular stone but is invisible to the opponent. Batoo became a short-lived fad among young people in Korea around 2011.Variants altering the rules of play
First capture
The first player to capture a stone wins. It was invented by Japanese professional Yasutoshi Yasuda, who describes it in his book Go As Communication. Yasuda was inspired by the need for a medium to address the problem of bullying in Japan, but soon found that "first capture" also works as an activity for senior citizens and even developmentally delayed individuals. He sees it as a game in its own right, not just as a prelude to Go, but also as a way to introduce simple concepts that lead to Go. For the latter purpose, he recommends progressing to "most capture", in which the player capturing the most stones wins. This variation is often called Atari Go in the West, where it is becoming increasingly popular as a preliminary means of introducing Go itself to beginners, since, afterward, it is natural to introduce the idea of capturing territory, not just the opponent's stones.Stoical Go
In Stoical Go, invented by abstract game designer Luis Bolaños Mures, standard ko rules don't apply. Instead, it's illegal to make a capture if your opponent made a capture on the previous move. All other rules are the same as in Go. Suicide of one or more stones is not allowed, and area scoring is used.All known forced Go cycles are impossible with this rule. The nature of the rule itself suggests that forced cycles are either impossible or astronomically rarer than they are in Go when the superko rule is not used.
Ko fights proceed in a similar manner to those of Go, with the difference that captures and moves answered by captures aren't valid ko threats. Although snapbacks are not possible in the basic variant, they can be explicitly allowed with an extra rule while retaining the property that all known forced cycles are impossible.
Environmental Go
Environmental Go, also called Coupon Go, invented by Elwyn Berlekamp, adds an element of mathematical precision to the game by compelling players to make quantitative decisions. In lieu of playing a stone, a player may take the highest remaining card from a pack of cards valued in steps of from to 20: the player's score will be the territory captured, plus the total value of cards taken. In effect, the players participate in a downward auction for the number of points they think sente | is worth at each stage in the game.The professional players Jiang Zhujiu and Rui Naiwei played the first Environmental Go game in April 1998. Since then the variant has seen little activity on the international scene.
Cards Go
In Cards Go players draw from a pack of cards contain instructions to play one of a fixed set of commonly occurring shapes. If the said shape cannot be placed on the board, then an illegal move is deemed to have been played, which necessitates resignation.Multi-player Go
In Multi-player Go, stones of different colors are used so that three or more players can play together. The rules must be somewhat altered to create balance in power, as those who play first have significant advantage.There are various optional rules that enable cooperation between the players, e.g. division of captured stones among neighbors, or forming alliances for adding up territory points.
A variant called parallel multiplayer go also exists, where the moves are announced simultaneously. If two moves overlap, they count as passes.
Paper and pencil go
Paper and pencil go is a Go variant that can be played with just paper and pencil. Unlike standard Go, games played under these rules are guaranteed to end in a finite number of moves, and no ko rule is needed. Nothing is ever rubbed out. It differs from standard Go in the following ways:- Surrounded stones are not captured, but just marked. Points occupied by marked stones count as territory for the surrounding player, but neither player can play on them for the remainder of the game. This implies that any group which touches a marked stone is unconditionally alive.
- Suicide is allowed, i.e., you can make a play such that one or more of your own stones become marked.
- Area scoring is used.
Omino Go