Go/Lesson 2: Basic Rules and Foundational concepts
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[edit] Basic Rules
[edit] Liberties
One very important concept in the game of Go is the concept of liberties. To count how many liberties a stone has you have to simply count how many free intersections, surrounding that stone, aren't occupied by other stones. So a lone stone in the middle of the board has four liberties (intersections placed diagonally to each other aren't connected), while a lone stone on the side of the goban has only three liberties and one placed in a corner has two.
Whenever an enemy stone occupies one of these intersections, the original stone loses one liberty (since the intersection isn't free anymore). It's also true that placing a stone of the same colour on an adjacent intersection reduces by 1 the liberties of the first stone, but they form a group, so their individual liberties aren't as valuable as before.
When two or more stones, of the same colour, are placed on adjacent intersections (remember, not diagonally) they form a group. When a group is formed, its liberties are now the sum of free intersections adjacent to any single stone composing the group itself. So two adjacent stones, in the middle of the board can have at most 6 liberties (three for each stone, since the fourth liberty is occupied by the other stone in the group). We can see that grouping stones is a good way to increase liberties.
[edit] Capturing Prisoners
To capture a stone, or a group of stones, one must completly cut off all of its liberties (in other words, the stone is surrounded on all four sides). Once a stone is captured, it becomes a prisoner. This is important, because for every stone captured a point is subtracted from that player's total amount of territory. Capturing works the same way with groups of stones — all captured stones are removed from the board and kept by the player who captured them. The area where the stones were removed from becomes the territory of the capturing player.
[edit] Atari
A stone with only one liberty is in "atari." This means the stone is vulnerable to capture in a single move by the opposing player. This is somewhat comparable to "check" in the game of Chess, but occurs more often and is "less important" to the overall strategy of the game. In Chess, when the King is in check, direct action must be taken to resolve this (e.g., the king must be moved out of check, another piece must move to block the attacking piece, or the attacking piece must be captured). In Go, there is no such requirement; when a stone is placed in atari, it is not necessary to respond at all. The stone can remain in atari for many moves, or be captured by the opposing player immediately, or protected by the attacked player immediately. When a stone is placed in atari, a player may see fit to attack another area of the board or continue working to capture other territory. A player placing an opponent's stone in atari is also not required to proclaim it, as is the rule in Chess.
Learn to recognize capturable stones and groups: Go/Capturing exercise
[edit] Ko rule
A ko is a shape (an arrangment of stones) where one player is able to capture exactly one of his opponent's stones with one move, but after capturing the stone his opponent is able to capture (in one move) the stone that was just played again, creating an opportunity for his opponent to capture that stone in the same way again. A ko fight (the fight to capture the territory made by a ko) can last indefinitely. This could be a problem and stop all progress in the game, so a rule was made to stop this from continuing. When player 1 takes a ko player 2 must play in another place before they can play at the ko again. this gives player 1 a chance to fill in the ko and stop the fight.
[edit] Handicaps
To balance a game being played between players of significantly different skill, the weaker player is sometimes granted a handicap of one or more "free" stones. Some rule sets (Chinese, New Zealand, etc.) allow these to be placed anywhere the player desires. Other rules (Japanese, e.g.) have predefined handicap placement. Placing handicap stones is treated as black's first move. one handicap stone is often given for every on rank difference between players. Thus if a player (white) with the rank of 7 kyu played a player (Black) with a rank of 12 kyu black would receive a handicap of 5 stones. though if the two players are only a rank or two different it is often unnecessary to use a handicap. If you or your opponent does not know their rank play an even game and if one player losses by more than a dozen points give them one stone and play another game. Repeat this until the proper handicap has been reached.
[edit] Foundational Concepts
[edit] Placing Stones
Stones are placed at the points created by the intersecting lines of the grid. A stone may be placed on any empty point, unless that point has no adjacent empty points and the placement does not cause the capture of adjacent enemy stone(s). The traditional way of placing stones on the board is by grasping the stone with the index and middle fingers, with the stone held horizontally between the index (below) and the middle (on top) fingers. This feels awkward the first few times it is done.
[edit] Surrounding Territory
Territory is surrounded when all of the liberties (the available moves immediately adjacent to a stone) of an area are controlled by a single color. Only an outline is needed to claim territory — placing stones at every point within an area will not claim teritory (and in fact reduces the actual territory claimed — the game is scored by counting open territory claimed, not spaces occupied by stones). An "eye" is one example of a group (joined stones) that claims territory. An opponent may play within territory if it is legal to do so.
[edit] Groups
[edit] Cutting
Cutting occurs when a stone is placed between two groups of enemy stones in order to prevent the groups from connecting.
[edit] Initiative (Sente - Gote)
Sente is when a player is "ahead" of his opponent if you will. It is when he forces the other player to respond to his moves. It is said that this player is in sente and his opponent in gote.
This section needs to be expanded.
[edit] Life and Death
A dead group is one that is unable to make more than one eye. Such a group is at risk of capture because it cannot be completely defended. A live group is one that is able to make two or more eyes. This is a very powerful group because the enemy cannot attack it successfully; any attack will result in immediate suicide or eventual capture of more territory or stones by the owner of the live group.
Groups can sometimes be neither completely dead nor completely alive.
[edit] Eyes
A single group of interconnected stones with one point of territory forms an eye. A group with two or more eyes cannot be captured, and is a powerful structure within the game.
[edit] Tsumego
[edit] Seki
A Seki situation happens when opposing groups are placed so that both players must sacrifice their own stones to occupy an uncontrolled point. Seki situations are always left alone until the end of a Go game. The free points in them are not counted when it's time to count for scoring.
[edit] Order of play
[edit] Exigent
First you should play the most urgent or necessary moves. These are the moves that could cause you to lose considerable amount of territory or weaken your position.
[edit] Exploit
If you can find no moves of the first type, you should look for ones that take advantage of an opponent's weakness. Also find what would be your opponent's urgent moves and block those, or otherwise take advantage of them.
[edit] Expand
If there are none of the first two types of moves then find the move that would take the most teritory or the biggest move.
