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BeginnerExercise2

 

Beginner Exercise 2 Solution
  Difficulty: Beginner   Keywords: Problem

[Diagram]
Solution

After B3, White can't play at a because of 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 two by three box. Apparently this is a popular example ...

Geoff: As a beginner, my guess was that the best place for Black to play would be the point marked W2 on the diagram, not the recommended B1. Is it obvious why my guess was wrong?

[Diagram]
Solution

Jasonred Ooh! Ooh! Geoff, let me answer this one for you! 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?



[Diagram]
Ko, but no cigar

Geoff: So either variation works out OK 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 W4 after B5, she might still live? Well, she can't because of the ko rule, but if she could find a large enough ko threat, she will play at W4 next and win.

So, we then have a ko fight.

After that, Black has to find another ko threat so that he can play on B5 again... and so on and so forth. With someone eventually running out of ko threats that are 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?

[Diagram]
Variation

If White answers with W2 here, Black plays B3. White would like to play at B3 as well, if Black plays at a or b. Why?


[Diagram]
Bulky five

Because if we add WC to the 2x3 square we get a shape called bulky five (marked). And that shape can be killed by playing on the vital point, marked with a square.


[Diagram]
Bulky five (again)

So, after B1 and W2 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 B3 next. (And that is why White trying to live with W2 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.
(OC) 2004 the Authors, published under the OpenContent License V1.0.