Editing Rules of Go (section)

== Optional rules ==

=== Compensation ===
To allow players of different skills to compete fairly, handicaps and ''komi'' are used. These are considered a part of the game and, unlike in many other games, they do not distort the nature of the game. Players at all levels employ handicaps to make the game more balanced.

==== Komi ====
{{Main|Komi (go)}}
In an "even", or non-handicap game, Black's initial advantage of moving first can be offset by ''komi'' (compensation points): a fixed number of points, agreed before the game, added to White's score at the end of the game. The correct value of komi (to properly compensate for Black's advantage) is controversial, but common values are 5.5, 6.5, or 7.5; the fractional value avoids a tied game. In a handicap game, komi is usually set to 0.5 (i.e., White wins if the game is tied). A handicap game with a handicap of 1 starts like an even game, but White receives only 0.5 komi (i.e., a White player who is stronger by one rank is handicapped only by Black's first-move advantage).

Before the 20th century, there was no komi system. When the great [[Honinbo Shusaku|Shusaku]] was once asked how an important game came out, he said simply, "I had Black", implying that victory was inevitable. As more people became aware of the significance of Black having the first move, komi was introduced. The amount of komi has been increased periodically based on analysis of game results indicating >50% wins for Black; each time, after a period of adjustment Black has again begun winning >50% of games. When it was introduced in Japanese Professional games, it was 4.5 points. However, Black still had a better chance to win, so komi was increased to 5.5 points in 1974. In 2002, the Japanese Go Association again increased the komi value to 6.5.

==== Handicap ====
{{Main|Go handicaps}}
Handicaps are given by allowing the weaker player to take Black and declaring White's first few moves as mandatory "pass" moves. In practice, this means that Black's first move is to place a certain number of stones (usually the number is equal to the difference in the players' ranks) on the board before allowing White to play. Traditionally, the [[List of Go terms|hoshi]] ("star points") – strategically important intersections marked with small dots—are used to place these handicap stones. On the {{nowrap|19 × 19}} board, there are nine star points: at the four 4–4 points in the corners, at the four 4–10 points along the sides, and one at the 10–10 point (the centre of the board, or ''tengen'' in Japanese). Smaller boards such as the {{nowrap|13 × 13}} and {{nowrap|9 × 9}} also have star points. The {{nowrap|13 × 13}} has 9 at the 4–4 points, 4–7 points, and the center. The {{nowrap|9 × 9}} board has only 5 points: the 3–3 points and the center.

When Black is only one rank weaker (also known as one ''stone'' weaker, due to the close relationship between ranks and the handicap system), Black is given the advantage of playing Black, perhaps without komi, but without any mandatory White passes. For rank differences from two through nine stones, the appropriate number of handicap stones are used. Beyond nine stones, the difference in strength between the players is usually considered great enough that the game is more a lesson where White teaches Black than a competition. Thus, nine stones is the nominal upper limit on handicap stones regardless of the difference in rank (although higher numbers of stones, up to 41 stones in some cases, may be given if the teacher wants a greater challenge).

=== Thinking times ===
{{Main|Go (board game)#Time control}}