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Beginner Exercise 2 Solution
White can't play at a because of damezumari (shortage of liberties). If White plays at b then Black answers at a. White can capture Black's stones, but that leaves her with a three in a row shape. KarlKnechtel: See also TwoByThreeBox. Apparently this is a popular example now. :) Geoff: As a beginner, my guess was that the best place for Black to play would be the point marked 2 on the diagram, not the recommended point marked 1. Is it obvious why my guess was wrong?
Jasonred Ooh! Ooh! Geoff, lemme answer this one for ya! After this sequence, I THINK a and b are miai for life! If black a, white b, if black b, white a!
To you seniors out there, am I right?
Geoff: So either variation works out okay for black, then? Fortunately I don't smoke, so lack of cigar is not a problem. Jasonred No, it leads to ko... notice that if white puts a stone on 4 after 5, he might still live? Well, he can't because of the ko rule, but if he could find a large enough ko threat, he will play on 4 next and win. After that, black has to find another ko threat so that he can play on 5 again... and so on and so forth. With someone eventually running out of ko threats big enough, at which point he will tenuki somewhere, and the winner of the ko duel plays on a... by the way, took me a while to get the concept of "ko duels"... And most importantly, the question says "kill white WITHOUT KO" Geoff Many thanks for pointing that out Jason. I was not thinking through the ko threat point properly. What if white plays somewhere else?
If White answers with 2 here, Black plays 3. White would like to play at 3 as well, if Black plays at a or b. Why?
Because if we add a white stone to the 2x3 square we get a shape called bulky five. And that shape can be killed by playing on that crucial "bottleneck" point, marked with a square. KarlKnechtel: You mean the vital point?
So, after 1 and 2 in the variation diagram, we have a bulky five shape, with one point already occupied by Black. However, the vital point marked with a square has not been played yet. That is why Black plays at 3 next. (And that is why White trying to live with 2 in the first diagram seems like a good idea - but fails as well.) Try to memorize the bulky five shape. It occurs over and over again. See also:
This is a copy of the living page "Beginner Exercise 2 Solution" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |