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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.
- 1 National variants
- 2 Variants altering the rules of play
- 3 Variants for more than two players, but not altering the mechanism of the game
- 4 Variants requiring memory of the position
- 5 Variants with limited knowledge of the position
- 6 Non-standard boards
- 7 See also
- 8 References
- 9 External links
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 is played on a 17×17 board, and starts with six stones (called Bo) from each color placed on the third line as shown. 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 (the 1-1 points) receives a bonus of 40 points, and if he controls the center point also, he receives a further bonus of 10 points.
Sunjang baduk is a different form of Go (baduk) that evolved in Korea. It has been played since at least the 7th century. Its most distinctive feature is the prescribed opening. The starting position dictates the placement of 16 stones (8 black, 8 white) as shown, and the first move is prescribed for Black at the center of the board. However, the counting system for determining territory at the end of the game also has some important differences. Namely, stones inside friendly territory, which are irrelevant to boundary definition, are removed before counting territory.
Batoo is a modern Korean variant. The name stems from a combination of the Korean words baduk and juntoo (“battle”). 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 has become very popular among young people in Korea.
Variants altering the rules of play
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.
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 his 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. On the other hand, snapbacks are not possible. Alternatively, though, rewording the rule to explicitly allow snapbacks still prevents all known forced cycles.
Environmental Go, invented by Elwyn Berlekamp, adds an element of mathematical precision to the game. In lieu of playing a stone, a player may take the highest remaining card from a pack of cards valued in steps of ½ from ½ 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.
Time Is Money Go
Each player begins the game with a decided upon amount of time (no byoyomi). At the end of the game, when the score is counted, the number of seconds remaining on each player's clock is added to his or her respective score.
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.
In Multi-player Go, stones of different colors are used so that four or more players can play on the same board. The rules must be somewhat altered to create balance in power, as the former players (especially the first four, on a four-cornered board) 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.
(Conventional Go can also be played on paper by drawing circles of different colors. Captured stones are marked with a line. Then if the square is replayed, a smaller circle is placed inside the larger circle.)
Also named Tetromino Go. Devised by R. Wayne Schmittberger, each player is allowed to play up to four stones in a turn, provided they are solidly connected on adjacent points. (There are five four-stone patterns possible, two three-stone patterns, and one two-stone pattern, ignoring rotations and reflections.) There is no komi; Black is restricted on his first turn to playing no more than two stones. The winner is determined by Chinese scoring: occupied and surrounded points each count 1 point; captured stones do not have point value. The inventor suggests a 15×15 square-celled board using square-tiled pieces.
Variants for more than two players, but not altering the mechanism of the game
This involves two teams of players taking either the Black or the White stones. Each player in the team must play in turn, playing out of sequence will normally result in a small penalty (usually three prisoners). Partners may not consult on how to play, or engage in any form of signaling. Communication between partners may only take the following forms listed below.
- May we resign? can be answered with yes or no
- How much time is left? can be answered with coded instructions for the next move. For example, the response 5 minutes and 13 seconds could be a hint to play at the co-ordinates 5-13.
- Whose turn is it?
Pair Go is a gender specific form of Rengo, calling for teams composed of one male and one female member. It was popularised by the Japan Pair Go Association as a means of increasing female participation in the game. They hoped that this increase in itself would add a new appeal to the game. The Ricoh Cup, the annual professional Pair Go world championship debuted in 1994. The International Pair Go Association sponsors an annual amateur world championship in Tokyo in November, which has been running uninterrupted since 1989. They first introduced the variant to Europe at the 1992 European Congress in Canterbury, England. Amateur Pair Go tournaments have been held in the United States at U.S. Go Congresses since 2005 at least  and in Denver, CO.
Variants requiring memory of the position
One (as a handicap) or both of the players cannot see the board in this variant. Therefore they have to remember the whole position. This is considered much more difficult than playing blind chess. Indeed, most club standard players can play blind chess, but only professional players are able to complete a game of blind 19×19 Go.
One Color Go
Both players use stones of the same color. This variation is regarded as a useful tool for developing one's reading skills.[clarification needed]
Variants with limited knowledge of the position
These variants are not purely strategic games, as the element of luck is quite important.
This game requires two players, a referee and three playing sets. Each player sees only his own board, while the referee can see them both and also has his own set. Players place stones on their boards, with no knowledge of what other players are doing. A referee keeps track of the game on the central board. If any player makes an illegal move, the referee informs him about it (some play that the referee says only that the move is illegal, while some, that the player is told whether the intersection is occupied or there is illegal ko capture). The player is allowed to make another move.
This is a crossover between rengo and shadow Go. There are two teams with two players each, a referee and five Go sets. The players move alternatingly as in rengo. Each player keeps track of their own moves on their own board; they are not informed about teammates' or opponents' moves. The referee keeps track of the complete game and informs a player if their move was illegal, in which case they can try again. The referee removes captured stones from all affected boards. Because of the asymmetry in information, this may be an undecidable game; which would mean that there is in principle no computer or algorithm that can tell from a given position who will win.
Although Go is most commonly played on a board with 19×19 lines, 9×9 and 13×13 boards are also available. They are used by beginners and by players who want a game that finishes more quickly. Due to flexibility of configuration, the two smaller sizes are more often played on the online Go servers such as KGS Go Server, and board sizes from 2×2 to 38×38 are also allowed.
Harald Schwarz invented a Go variant that is played on a circular lattice.
A toroidal board is two dimensional surface with an implied third dimension because it is as if a standard board has been rolled and two opposite edges joined to form a tube and then the ends of the tube joined. It can be simulated on a standard 19×19 board, but requires imagination on the part of the players to perform an abstract join at the edges. It is noteworthy that the toroidal board has no corners, so standard joseki do not apply. This kind of variant can also be performed with three other identifications, see Surface construction from polygons.
TriGo is a go variant that uses a triangular-grid goban, where each stone has up to six liberties. To compensate for this, there are several rule changes: ko and superko are limited in scope, komi is not used, and after the first stone is placed, every turn consists of placing two stones. After both players have passed a turn, the score is counted (the sum of captured stones and territory), and in the case of a draw the player passing first wins.
Other than 2D
Alak is a Go-like game restricted to a single spatial dimension. Go can be extended to three dimensions. One example is Diamond Go, which uses the structure of a carbon diamond crystal lattice. With many such Go variants, the nature of the game changes dramatically the standard 4-connectivity of the points is changed, however, Diamond Go maintains this connectivity. Another example is Margo, by Cameron Browne, a variant played with marbles that can be stacked on top of one another.
A program called Freed Go can be used to play with boards with generic topology. It has embedded 11 different boards, either three-dimensional shapes (including cube, sphere, cylinder, diamond, torus and Möbius strip) or flat fields with points connected to three, five or six neighboring points, but it's also possible to create custom boards.
- Abstract strategy game for other board games sometimes compared to Go
- Games played with Go equipment
- Tibetan Go (Sensei's Library)
- Bangneki (Sensei's Library)
- Hong, Sung-Hwa (1999). First Kyu. Good Move Press. ISBN 978-0-9644796-9-2.
- Stoical Go (Sensei's Library)
- Coupon Go | School of Mathematics
- Environmental Go (Sensei's Library)
- Cards Go (Sensei's Library)
- Paper and Pencil Go (Sensei's Library)
- Senseis Paper Go PDFs
- Schmittberger, R. Wayne (1992). New Rules for Classic Games. John Wiley & Sons Inc. pp. 62–64. ISBN 978-0471536215.
- Pair Go
- Ricoh Cup Past Results
- Pair Go amateur world championship
- U.S. Go Congress 2005
- Bob High, Deviant Go, The American Go Journal, Volume 24:1 Winter 1990
- Ewen Callaway, Computers conquer the final frontier in board games, February 14, 2009
- The Milton Keynes Go Board
- Page about the circular lattice Go board
- Diamond Go
- Freed Go 1.1 - The Game of Go in 3D
- The North American pair go circuit
- Go Variants at World of Abstract Games, with sections on Other Rules, Other Boards, Other Pieces, and Other players; well illustrated
- Go Variants, by Andre Engels, text descriptions
- Topological Go, including a mathematical discussion
- Sensei's Go variants on Sensei's Library
- Freed Go, board with generic topology
- World Batoo League