Harleqin wrote:
Ah, OK, my understanding of button was “if white makes the last move, she gains one point’.
Ah, that makes sense.
![Smile :)](./images/smilies/icon_e_smile.gif)
So the thing is, these three are exactly identical:
A: 7 komi, the button is worth 0.5 points to the player who spends a move to take it.
B: 6.5 komi, if white spends a move to take the button, white gains a point.
C: 7.5 komi, if black spends a move to take the button, black gains a point.
At least for me, even though these are literally identical in all cases, I intuitively find stating it as in B and C to be weirdly asymmetric and confusing. Stating it as in A makes it more obvious that the button is simply a move with a particular value, and that when the game is as close as possible, it functions as a tiebreaker to the player able to end in sente for normal board plays (or who is a ko-monster with enough threats to take the button before finishing a final ko). It also generalizes better to coupon Go / environmental Go:
https://senseis.xmp.net/?EnvironmentalGo.
Note that we use "spends a move to take the button" rather than a formulation that talks about who "is the first to pass". The button should ideally not be considered to be a pass, because it may lead to some oddities rarely in some rules if the action of taking the button, a move that actually has value, is conflated with "I have nothing to do and wish to end the game", and also the act of taking the button should also be considered to change the game state so that it makes retaking a ko afterwards to be legal. For similar reasons "spends a move to take the button" is probably better than a formulation that talks about who "makes the last move". To avoid pathologies, you probably want the button to behave as much as possible like an ordinary extra possible move on the board that is gote and worth 0.5 points to the player who can take it.