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BeginnerExercise142

 

Beginner Exercise 142 Attempts
  Difficulty: Beginner   Keywords: Problem

[Diagram]
White to play.

Zephi: This one seems a bit complicated, but I can see at least two possibilities. Focusing on only the two marked stones, white needs B to keep them from escaping, but can't play there without being immediately captured, so I think white would have to first set up a ko at point A. After this, I think that B and C are miai for capturing, though white would need some good ko threats to make B work. Here's how I think both cases would look:


[Diagram]
Black blocks the ko

Black looks pretty dead if he just connects to avoid the ko.


[Diagram]
Black allows the ko

In this case, black takes first in the ko, so white needs to have some really good ko threats to make this work.


[Diagram]
White plays b first.

Again, Black takes first, and white needs a very good ko threat. (W3 seems like it would only cause black to fill in the ko in which case, playing at c is no longer an option for white.)

Well, if this isn't the solution, I hope it's at least on the right track.



Malweth: Going with your last diagram, White does take ko first. If W4 instead elsewhere, B5 at W4 kills.

[Diagram]
W5 at 1.

[Diagram]
Shortage of liberties.

unkx80: Sorry, but Zephi's solution is correct. In your diagram, B4 can connect, but W5 cannot play at a without putting himself into self-atari.



Malweth: I'll take the easier path (I think...)

[Diagram]
Wrong answer!

[Diagram]
Right answer? White has a 2 step ko to live.

unkx80: I would say, White's play is sub-optimal. But you are almost there already. =)

Malweth: I see, I think... White would do better to save the E19 group.


[Diagram]
White saves E19 rather than B18


ChrisSchack: I think W4 looks odd in the two-step ko ... why give B the chance to take first?

[Diagram]
Better play?

W need only ignore a single threat to play a, winning the ko. No need to connect to the other side, they're already alive. B has a direct ko, but has to make the first threat.

On second thought, why not take B1, it's extra points...



This is a copy of the living page "Beginner Exercise 142 Attempts" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.