Various tales are told of its origins, including one which says that the game was created by a Chinese emperor to teach his son strategy.
The game is played on a flat wooden board, rectangular in shape, with a square grid painted upon the top. It is usual for the full game to be played on a 19x19 board (i.e. one with 19 lines to a side) but this is not fixed and many players also enjoy playing on 9x9 and 13x13 boards.
The rules of the game are very simple:
1) There are two players, one is Black, the other White. Each has a quantity of small pieces called "stones". Black plays first, except where the game is played with a handicap (see later).
2) Each player takes a turn to either place a stone upon an unoccupied point of the board or pass. Pieces are played on the intersections of the gridlines (not in the squares).
3) Each stone has a number of "liberties" which is equal to the number of unoccupied points adjacent to the stone. Only points connected to the point which the stone is occupying by the lines of the grid are adjacent - e.g. diagonals do NOT count.
Stones of the same colour occupying adjacent points of the board are connected into a group. Stones in a group share their liberties and are irrevocably connected.
4) If a stone (or group of stones) is surrounded on all sides it (they) is (are) captured and removed from the board. This is the only situation in which stones can move once they have been placed.
5) In only two cases is it forbidden to play upon an unoccupied point:
i) Suicide is not permitted. Thus a stone cannot be played where it
would have no liberties, nor added to a group such that it would have no liberties.
ii) The board may not be returned to the state it was in at the end of
your last turn. This is known as the ko rule and has important implications (and DEFINITELY needs a diagram). It arises in a situation in which an opponent captures one (and only one) of your stones and you are immediately in a position to recapture. By the ko rule you are forbidden to do so, and must play somewhere else first.
6) Play stops after two passes (e.g. by consensus).
So, those are the rules. So where's the game? How do you win?
Unfortunately it is rather difficult to answer those questions unless you've tried playing it, but in order to attempt this two further principles must be explained:
A) Groups can be made uncapturable. This follows from rules 2 and 5(i), and the reasoning goes like this: Since a player may only play one stone at a time and cannot commit suicide it is impossible to take all of the liberties of any group which contains two (or more) empty spaces in which it would be suicide for the opponent to play, as to do so would require the placement of two stones simultaneously (it should be noted here that having only one such space would not guarantee the safety of a group as if the group were reduced to a state in
which this space were its only liberty the opponent would not be commiting suicide by playing there as to do so would capture the group). A group which is in such a state or can easily and incontravertibly (assuming at least some rationality on the part of the player) reach such a state is 'alive' and is said to have two eyes (me in japanese).
This principle is exceptionally important, and forms the basis of the strategy of the game.
B) If a player surrounds an empty area with an uncapturable group such that their opponent is unable to form a living group within that area, that area is known as the players "territory".
Obviously this is a very loose definition in a sense, and it is very much a matter of judgement as to whether an area is regarded as territory - this is why the game ends by consensus. Beginning players frequently play out situations to the bitter end as they have not yet developed a sense of how much space and influence are required to form a living group. Professional play, however, can be puzzling to weaker players as it leaves many situations apparently unresolved.
Now that the principles of the game have been developed from the rules, the aim of the game can be stated: The winner of the game is the player who has the most territory once two consecutive passes have been made.
There are many different ways of scoring this, the following (as an example) is the Japanese method:
i) Stones within territory are removed and given to the player to whom the territory belongs, as they are captured.
ii) Each player places their captives in the opposing players territory.
iii) The remaining territory is counted. This is usually achieved by
rearranging the board such that the shapes of the territories are easily countable.
iv) If appropriate, extra points are added to whites score. This is
usually done in non-handicap games as a means of offsetting the advantage black gains by going first and is called komi. The actual value of whites komi can vary, but it is usually done in half-points in order to prevent the game being a draw. Values of about 4.5-6.5 are quite common, although the komi may be as low as half a point.
The winner is thus the player with the highest score once the balance of territory and captives is calculated and any appropriate komi has been added.
I am sure that this all sounds rather arcane (hopefully some pictures might one day be available - until then see www.britgo.org) and not in the least enjoyable. Please believe me when I say that this is wrong, in every
fundamental respect, although of course it isn't everyone's cup of tea.
The actual strategy of the game is vastly more complex than this, and (if this article or something very like it interests anyone) is a possibility for a follow-up article. I am aware that this does not come across very well without pictures, but I feel very strongly that the Guide should contain an entry on Go.