2 player game of GO
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About 2 player GO - How to play - Points
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In the archive you can see all published games and see them re-played. You can also manage your own played games and publish them for others to learn from.

Challenge your friends
You can challenge your friends to a game by first signing in (as guest or registered) and creating a game. After you create a game you will be given a url for this page and a 4 character key. If you send the url and 4 character key to someone they can join your game by signing in and entering the 4 characters in the "Accept challenge" window. If you send the key to more than one, only the first to accept will join the game.
If you like you can accept the challenge yourself and play solo.
The game of Go
Go originated in China 3000 years ago or maybe more and spread through Asia and the rest of the world. It is usually played on a board with a grid of 19 by 19 but beginners may play on 9 by 9 or 13 by 13.
The game consists of two players each assigned a colour, black vs white, Black always plays first and the object of the game is to control as large an area (empty spaces encircled by ones own colour) on the board as possible when the game ends.
Enemy pieces can be removed from the board (are taken prisoners) by encircling the enemy shape (pieces of the same colour connected horizontally or vertically) so that the shape has no empty space anywhere around or inside it.
The game goes on till both players pass consecutively.

If you are completely new to the game of Go you can have a look at some of these references:
http://intergofed.org/ (international go federation)
To practise some "life and death problems" you can visit:
The point system in Go is quite challenging for a computer (or, more precisely, for a programmer with my humble skills). As I understand it there are two basic systems for tallying up points: the Chinese way and the Japanese way.
Chinese points (for each colour): pieces on the board + area controlled (+ komi for white)
Japanese points (for each colour): prisoners taken + area controlled (+ komi for white)
Thus at the end of a game you are shown two point tables, usually with the same winner.

How this programmed point system works
To programatically count points all pieces on the board are first divided into shapes. Next step is to classify the shapes' status: "alive", "unconditionally alive", "dead" or "seki". Lastly the empty areas are also identified and assigned to a colour still alive that surrounds them completely.
Pieces of the same colour connected vertically or horizontally (diagonals do not count).
Since a game does not end until both players see no need to play further and pass consecutively it seems fair to assume all shapes still on the board are alive. Thus, shapes are deemed alive until proven otherwise in the following programme tests.
Unconditionally alive:
A shape is unconditionally alive if the shapes' colour does nothing but pass while the opposing colour plays all possible positions recursively and is still not able to capture the shape (suicide counting as an illegal move).
If a shape 'X' has 4 liberties or less it is assumed dead if: X is not unconditionally alive, all surrounding enemy shapes have more liberties than X or are unconditionally alive, X cannot connect to friendly shapes (in one move) who are not dead themselves.
Seki is a special condition where there is a stalemate in an area. Here it is determined as seki if neither side can make the first move in an area without dying in the opponents immediate response.

Use the point table and point markers on the board as a reference, but take a look at the board yourself and confer with your opponent. Unconditional and seki definitions should be quite certain, however the definition of dead shapes, in this programme, is weak as there could easily be dead shapes with more than 4 liberties, however, with more than 4 liberties, it is easy to disagree on the shape status and the situation may be best resolved simply by playing it out.
The empty areas are also a bit fragile as they are assigned to a colour only if the empty space is completely surrounded by one and only one colour.