: ( 648gm)
Black captures White's single stone in the upper right.

In principle, Black loses two Main Semeai Liberties by this move. But becomes an approach-move liberty of his group, so the net effect of this move is a loss of one Main Semeai Liberty.

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White's wedge in the left centre is her strongest answer to Black's tenuki in that area.

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In principle, this kikashi should be left unplayed and kept as a potential ko threat.

Here in this line, however, Black already lost two of his potential ko threats by playing some of his own kikashi (, ) "early", compensating for our technical mistake mentioned above.

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White plays Dany's atekomi, intending to start Dany's Ko a few moves later.

Please note that this move is played outside the Main Semeai, but does not lose a tempo therein, because becomes an approach-move liberty of White's group at the left.

Black is still par with the Punishment Semeai Liberty Level.

Black is unable to continue with , or , in the left centre, because any of these moves would push him below the Punishment Semeai Liberty Level.
On the other hand, White threatens the severe cut at , which would win her the game.

Black is strictly bound to continue with the Main Semeai. Therefore, giving atari at is his only choice, because this move is the only one that also defends against White's cut at (which White will not play now; please refer to this subvariation 648of for details).

White will connect at , providing Black with two Main Semeai Liberties. Now, Black is able to defend against White's cut at .

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Black's solid connection in the left centre simplifies the issue.

Black lost his third potential ko threat by his just played kikashi , in the lower left, so it does not make sense to start Dany's Ko with the atari at , instead.
White is comfortably ahead in ko threats (9 x vs. 6 x slB).

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White plays her kikashi in the lower left corner.

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White's connection is the last valuable point outside the Main Semeai remaining on the board.

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Black continues with the Main Semeai.

Black plays 3/3 reductions.

Capture Variation:

Compared to the superordinate variation ...

• White's cumulated gain at the upper edge is two points.
• Black captured an additional White stone in the left centre, but did not get any territory there, losing one point, so the net effect is zero.
• Black's cumulated loss in the lower left corner is two points.
• Black destroyed two points of White's territory in the upper right.
• Black captured White's single stone there, so gaining two points.

In total, gains and losses compensate for each other.

White + 2 => White + 2

Semeai Variation:

Compared to the superordinate variation ...

• White's cumulated gain at the upper edge is two points.
• Black captured an additional White stone in the left centre, but did not get any territory there, losing one point, so the net effect is zero.
• Black's cumulated loss in the lower left corner is two points.
• Black captured an additional White stone in the lower left corner, but one White stone less in the left centre, so the net effect is zero.
• White captured an additional two Black stones in the upper right, so gaining three points.
• White did not get one point of territory in the upper right corner.

In total, Black lost six points.

Black + 4 => White + 2