(Referenced by 503; 566k)

During the move sequence that follows the tsuke of Yamada Shinki in the upper left corner, KataGo suggested White playing the crosscut immediately.

As with the tsuke itself, Black has no real resistance at his disposal and has to surrender passively, losing another three points of territory.

We were very surprised that KataGo preferred the crosscut of (after Yamada's tsuke = , ) to drawing-back with a move at .

On the other hand, this move might be standard endgame repertoire that we amateurs were absolutely not aware of.

Black's atari at starts KataGo's preferred continuation.

Black might want to resist more forcefully, by giving atari at instead.

The endgame continues on the lower edge with White's "usual" move at .

Eventually, White is her bad-shape move in the left centre that costs Black one point.

For the sake of simplicity for calculation, let us assume these moves here, which might not necessarily be played in order.

White's connection at is not related to the Main Semeai, so White loses a move therein. Therefore, Black is able to play an additional forcing move at the right, e.g. at .

Compared to Our Solution, ...

– White gained two additional points of territory at the upper edge ().

– White gained another two points by destroying Black territory in the top left corner ().

– Black gained two points by his forcing moves in the centre and at the top right ().

In total, White gained two points, so eventually

White will win the Capture Variation by two points.

Please note that White's local gain by playing KataGo's crosscut is three points. (There might be variations where Black is unable to play some territory destroying move in the upper right, due to the negative effect of such moves on the Semeai Variation.)

In reality, White will continue the Main Semeai by connecting at , instead of connecting her single stone at the upper edge that is in atari.

This gives Black the opportunity to capture White's single stone at the top with .

White is able to block immediately at . Both sides played one move outside the Main Semeai, so nothing serious happened.

After the hanezeki has been resolved, White will capture with . Black will be unable to win the final ko, so White will connect with .

Compared to the variation shown above, either side gained one point (, ), so the result of the game remains the same as before.

White will win the Capture Variation by two points.

Black might want to resist more forcefully, with giving atari at .

After White's atari at , Black captures White's single stone with , entering what might be called a "peaceful" sequence.

If Black wanted to fight a ko, he would connect at instead.

After the exchange of White for Black , White connects her -stone out, while Black secures life for his group in the corner.

Black must be on his guard hereafter, as White created an approach-move liberty in his formation, at .

Black connects at , so eliminating his weakness.

Without this move (or another one that protect the cutting point), Black will be unable to occupy both of White's liberties at and .

Otherwise, White would give atari at , and Black cannot connect, due to a White move at .

White starts the further endgame on the left side of the board.

The top is already played out, so Black can connect at .

The exchange of White for Black is inserted for scoring purposes only. In the "real" game, these moves would be played later.

Compared to KataGo's preferred line of play, ...

– White gained nine points in the top left corner (, , ), by reducing Black's territory as well as saving her single stone in the corner.

– White gained two points of territory at the top ().

– Black gained three points of territory in the top left corner ().

– Black gained four points at the top, by destroying White territory (, ) and saving his stone ).

– Black gained two points at the bottom, by connecting his stone ().

In total, White gained one point, so ...

White will win the Capture Variation by three points.

Black connects at , intending to start a ko fight, but which he will be unable to win.

After White's atari at , Black might want to give counter-atari at , instead of capturing at .

Black attaches at , in order to block White's access to the corner.

Cutting at (or ) will not lead to a better result.

White's hane at prepares for the ko at / .

White's ko threat at utilises Black's "new" weakness in the centre.

Black connects, making the ko a direct one for both sides.

Black's ko threat at threatens to live in the top right by capturing White's stones below.

However, the value of this threat is much too small, so White ends the ko fight by capturing at .

Black secures life at the top right, but White kills Black's top left corner in return.

Black, for his part, cannot kill White's top right corner.

White does not need to capture the tail, and so is ahead by a very large margin.

Even if the hanezeki exchange (, ) had not been played, Black would be short of ko threats.

White also has at least two at the points of .

Additionally, capturing the nakade and / or the tail, with moves at , will be a source of a large number of White ko threats.

On the other hand, Black moves at any of the points of are no valid ko threats, as White intends to capture the tail anyway. And she will do so in sente.

Black cuts immediately with a move at that is also an atari.

White tries to live in the corner by blocking at , and Black connects his troops by capturing with .

White's descent to and reduce Black's group to only one eye.

Black returns the favour to White's group with the placement at .

White gives atari at , where after Black starts a ko fight.

However, Black will be unable to win this fight, due to White's ko threats at in the centre and those moves of the Main Semeai after capturing the nakade or the tail (with moves at ) that can be used as ko threats for White.

Black gives double-atari at .

White captures a Black stone.

Black is another double-atari.

White gives counter-atari at , starting a ko fight.

We already know White's ko threat at in the centre.

Black reduces White's eye space in the corner.

White is another ko threat in the centre of the board.

Black connects at , because he cannot allow White to capture his single stone above.

White's third ko threat in the centre.

Black reduces White's eye space in the corner.

White finishes this ko fight, and Black connects his troops by capturing at .

However, there is still a ko fight to come ...

White's throw-in at spoils Black's shape.

Even after Black captures with , Black's group cannot get more than false eyes.

White's throw-in at prevents a Black eye in the corner.

Black prepares the scene for a ko fight.

This ko fight starts with .

Black's push at should not be played as a ko threat, because it loses one decisive liberty in the Main Semeai, resulting in White winning the Punishment Semeai.

But KataGo does not mind, as it is very sure to win anyway, and continues with participating in the ko fight.

Ignoring White's connection at (as far as the Main Semeai is concerned) by giving atari at in the top left corner results in being two moves behind in the Main Semeai.

White's atari at gives Black one move back in the Main Semeai.

White starts using moves from the Main Semeai as ko threats, starting with capturing Black's nakade at the left with .

Black has to follow the Nakade Sequence by playing the placement of .

Again, White's atari at loses one liberty in the Main Semeai, so the liberty relationship is at par now.

Please note that if White followed the Main Semeai, instead, Black needed to capture at and at before he was able to take White's liberty at the point of , therefore losing another two moves in the Main Semeai. Black would be hopelessly three moves behind.

Black's throw-in at loses one liberty in the Main Semeai. Black is now behind by one move again, so he will suffer from the Punishment Semeai.

Trying to reduce White's group on the lower edge to only one eye with Black is no valid ko threat, in principle, as White intends to capture the tail anyway.

Ignoring this move would put White ahead by two moves in the Main Semeai.

White is her last ko threat in the nakade.

Black's atari at loses one liberty in the Main Semeai. Now, Black is fatally behind by two moves again.

Again, a White atari – this time at – loses one liberty in the Main Semeai, so Black is back at being behind by "only" one move.

Michael Redmond's kikashi in the bamboo joint does not change the liberty relationship in the Main Semeai here, as White is able to connect at without leaving an approach-move liberty behind.

Black does not have any effective ko threat left, so he finishes the ko by capturing White's group in the top left corner with .

Black would have two effective ko threats left, had he not played the Hanezeki Exchange (, ) before. In this case, he might have answered White's ko threat locally with a move at .

White, however, had another ko threat in the centre, at , and several ko threats in the lower right corner, starting with capturing the tail with a move at .

We can reason that Black never has the slightest chance to win a ko fight in the top left corner.

White captures Black's two cutting stones in the centre with , so capturing the tail will become obsolete.

Black's territory is concentrated in the top left and bottom left corners; White wins the game by a very large margin.