3

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I thought I had lost, but Cosumi says that I (white) won the game (I think by 27 points).

I don't see how those 7 black stones are prisoners rather than the adjacent 4 white stones.

Am I missing something?

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  • Cosumi is simply wrong. If both players have passed then this scoring doesn't make sense. But it's true that in this case, White could have captured the five stones instead of passing.
    – Stef
    Jul 22, 2023 at 17:05

2 Answers 2

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This game isn't really finished - there are still moves available that gain points.

If it's your turn, playing in the center and then extending upward if Black connects will capture at least the five stones that are transparent. Once you've done that, the four white stones to the right will be safe, and you can capture two more black stones by sacrificing one along the edge.

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  • 1
    Ah, right. I didn't realize I had played the game so intelligently :-) Jul 8, 2023 at 13:07
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    I agree that white can continue, but I don't think w can capture 5. Black has 2 stones in atari at the top, so the 5 black stones should live. However, after this, white can cut on the left side (3-7 point) and black will lose 2 stones at the edge. So the transparent stones are all alive, but the 2 black stones on the left should die.
    – mafu
    Jul 9, 2023 at 11:46
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    I think if Black plays that way, White can throw in and squeeze and then get the four stones on the left. I don't think it's better for Black.
    – TimK
    Jul 9, 2023 at 20:48
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    @mafu the two white stones at the top just below 1 click are captured no matter whose turn it is. However that doesn't affect the 5 transparent black stones in the center. If it is white to move white can play at the very center of the board and capture them. If it is black to move black can save these stones.
    – quarague
    Jul 11, 2023 at 16:29
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This is an intriguing position. TimK already explained that a white move at F6 will capture 5 black stones and that this is not because black cannot save them, but because saving them would lead to desaster.

To illustrate his answer, at first, it looks like white cannot do anything because the stones at H11 are in atari. However, if white forces black into a dumpling shape and to capture them, white can then cut at C7 and black is in trouble.

sequence

(5 at 8)

Per TimK, at this point, the black-10 group is in fact captured: Black cannot capture white-11, nor can he capture D9. This is a complete collapse.

The best endgame after white-1 might be, as TimK suggests, to simply answer white-1 at white-3, sacrificing 5 stones. Then black must next protect the cut by playing at E7. This gives white time to capture L7 via throw-in. In total, white wins by 20 points.

I do not see any other resistance for black that would achieve a better result.

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