Imagist/Problem 5 Solution

Sub-page of Imagist
Black to play  

The black+circle and white+circle groups are in a capturing race. Both groups have four liberties[1] and it is black's turn, so black should be able to win the capturing race.


However, if black begins filling outside liberties as normal, he runs into shortage of liberties. If black plays B1 at W4, treating it as a necessary approach move, both groups still have four liberties and it is now white's turn, so black loses.


If black plays this B3 and allows white to capture B1, white must spend another move to capture W4, and the result is not even ko, since black cannot play x due to shortage of liberties.


B1 is tesuji-ish, threatening to connect out while reducing a liberty. W2 does not gain any liberties, so it is okay that B3 reduces liberties for both groups. This is interesting because normally shared liberties should be filled last. Now when white reduces liberties at W4 (or white a) B5 is does not require an approach move at b because it is atari on white's group.

Tesuji-ish (variation)  

If white plays this W2, attempting to connect out, black simply connects himself with B3. When white plays W4 or W4 at a, B5 is atari and white doesn't have time to connect.


It may seem that B1 and B3 can be switched in the first solution diagram, but B3 only works because of W2 (from the solution diagram). If black reduces a shared liberty first, white simply reduces black's outside liberties and wins.

Tesuji-ish, but!  

Bill: Oh, ye of little faith! W4 saves the day.

Approach Ko  

Bill: Black can make an approach ko this way. W2 threatens to play at B3, so Black does not have time to connect at W4.

Ko, too  

Bill: W2 can make ko, too, but Black takes it first, and it is a direct ko.


Bill: You mean dame.

Imagist/Problem 5 Solution last edited by Bill on April 12, 2007 - 20:43
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