Editing Go (game) (section)

== Overview ==
[[File:Fineart vs Golaxy.gif|thumb|The first 150 moves of a Go game animated. (Click on the board to restart the animation in a larger window.)]]

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.{{sfn|Matthews|2004|p=2}} 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 a formation 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 (called "eyes"). Another essential component 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.

[[File:Golibs.png|thumb|The illustration [A] displays the four "liberties" (adjacent empty points) of a single black stone. Illustrations [B], [C], and [D] show White reducing those liberties progressively by one. In [D], when Black has only one liberty left, that stone is under attack and about to be captured and eliminated (a state called ''atari'').{{sfn|Cobb|2002|p=12}} White may capture that stone (remove it from the board) with a play on its last liberty (at D-1).]]
Initially the board is bare, and players alternate turns to place 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), as well as threaten to capture their opponent's stones and formations. Stones have both offensive and defensive characteristics, depending on the situation.

An essential concept is that a formation of stones must have, or be capable of making, at least two enclosed open points known as [[List of Go terms#Eyes|''eyes'']] to preserve itself from being captured. A formation having at least two eyes cannot be captured, even after it is surrounded by the opponent on the outside,{{sfn|Iwamoto|1977|p=77}} because each eye constitutes a [[List of Go terms#Liberty|''liberty'']] that must be filled by the opponent as the final step in capture. A formation having two or more eyes is said to be unconditionally [[#Life and death|''alive'']],{{sfn|Cho Chikun|1997|p=21}} so it can evade capture indefinitely, and a group that cannot form two eyes is said to be ''dead'' and can be captured.

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 and death|life status]] of one's own groups.{{sfn|Cho Chikun|1997|p=28}}{{sfn|Cobb|2002|p=21}} The liberties of groups are countable. Situations where mutually opposing groups must capture each other or die are called capturing races, or [[Capturing race|semeai]].{{sfn|Cho Chikun|1997|p=69}} In a capturing race, the group with more liberties will ultimately be able to capture the opponent's stones.{{sfn|Cho Chikun|1997|p=69}}{{sfn|Cobb|2002|p=20}}{{efn|Eyes and other complications may need to be considered when counting liberties}} 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.<ref>{{cite web|title=KGS Go Tutorial: Game End|url=https://www.gokgs.com/tutorial/gameEnd.jsp|publisher=KGS|access-date=5 June 2014}}</ref> The game ends when both players pass{{sfn|Cho Chikun|1997|p=35}} 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|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.{{sfn|Cho Chikun|1997|p=107}} Players usually start near the corners because establishing territory is easier with the aid of two edges of the board.{{sfn|Iwamoto|1977|p=93}} Established corner opening sequences are called [[joseki]] and are often studied independently.{{sfn|Cho Chikun|1997|p=119}} However, in the mid-game, stone groups must also reach in towards the large central area of the board to capture more territory.

[[List of Go terms#Dame|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. [[List of Go terms#Seki|Seki]] are mutually alive pairs of white and black groups where neither has two eyes.

''Ko'' (Chinese and Japanese: {{lang|zh|劫}}) 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.{{Sfn|Cho Chikun|1997|p=33}} 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.{{sfn|Cho Chikun|1997|p=37}} In Japanese, it is called a ''[[hanami]]'' ko.<ref>{{cite web|url=http://senseis.xmp.net/?HanamiKo |title=Hanami Ko at Sensei's Library |publisher=Senseis.xmp.net |date=2013-01-09 |access-date=2014-03-25}}</ref>

Playing with others usually requires a knowledge of each player's strength, indicated by the player's [[go rank|rank]] (increasing from 30&nbsp;kyu to 1&nbsp;kyu, then 1&nbsp;dan to 7&nbsp;dan, then 1&nbsp;dan pro to 9&nbsp;dan pro). A difference in rank may be compensated by a handicap—Black is allowed to place two or more stones on the board to compensate for White's greater strength.{{sfn|Iwamoto|1977|p=109}}{{sfn|Cho Chikun|1997|p=91}} 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 ===
{{more citations needed section|date=February 2016}}
{{Main|Go terms}}
Basic strategic aspects include the following:
* Connection: Keeping one's own stones connected means that fewer groups need to make living shape, and one 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.<ref name=":0">{{Citation|last=Baker|first=Karl|title=The Way to Go: How to Play the Asian Game of Go|year=2008|orig-year=1986|url= http://www.usgo-archive.org/files/pdf/W2Go4E-book.pdf|edition=7th|publisher=American Go Association|location=New York, NY|archive-url=https://web.archive.org/web/20121203014424/http://www.usgo.org/files/pdf/W2Go4E-book.pdf|archive-date=December 3, 2012|url-status=live}}</ref> An opponent cannot fill in either eye, as any such move is suicidal and prohibited in the rules.
* 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: Set up a new living group inside an area where the opponent has greater influence, means one reduces the 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 ([[Go terms|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.