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A set of 9 problems were presented at the Bracknell 2000 tournament, 8 were Go and one was Origami. This was the last & hardest Go problem, "Black to connect his stones on the right to the group at the bottom" (although it wasn't phrased like this).
When you have solved the Bracknell problem, show that Black A is wrong. I found this surprisingly difficult to do.
A subsidiary question: once the Black groups are connected, how stable is the White group in the corner? Is there anything Black can do to it?
The answer that seems to occur to most people first is either A in Dia 1 or the clamp above A. It can readily been shown that the clamp fails - White just extends up to diagonally join his line of three. You have to stop this connection, so that determines Black 1.
There are only two plausible White 2s. White 2' at A is cleanly refuted by the net Black 3' at B. The White 2 shown is trickier to deal with and it turns out that the net at 3 is the move.
When studying the problem, people seem to instinctively investigate White 4' at 4, 8 and when these are refuted 9 - none of these are the strongest though.
Dia 3 shows a typical sequence where straightforward replies keep the White liberties down to a low number and capture. Note that White could play 10' at 11 to escape with the top half of the surrounded White stones, but that Black 11' at 10 rescues the Black stones on the right.
For some reason White 4' at 12 escapes notice. It is the hardest to refute.
In Dia 4, Black 5 is forced. If Black plays 5' elsewhere, White 6' is played at 5 and White has escaped out to the left. The bulk of the White group has too many liberties, even with throw-ins, to be caught in damezumari.
6, 7 and 8 are 'obvious'.
There is a strange blind spot - at least amongst West Surrey memebers - which wants to insist that there is no alternative to 9 in Dia 5. We spent ages trying various weird sequences to stop White escaping but they all failed. Dia 5 is typical.
One correct move is to play 9 in Dia 6. You can't capture all the white stones, but there is time to capture the cutting bottom four.
Since I wrote the previous paragraph, I have discovered that Black can connect at 9 in Dia 5, as long as he responds to the atari of Black 10 by playing 11' at 16. Again Black captures the lower four white stones.
The second question, "Why is Black 1 at A in Dia 1 wrong" is shown in Dia 7.
If Black tries the tactic of Dia 6, playing Black 11' at 16, White 12' captures at 11 and there is no White shortage of liberties available to aid Black.
I don't intend to go into details on this, but the White group is secure and lives with territory whatever Black does. If there were a Black stone at the lower 5-2 point it would be different - the right 3-1 point leads to 2 kos - but there isn't such a stone.
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British Go Association
Last updated 2004-08-10
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