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KanazawaSolution24
KanazawaSolution69
KyuExercise4Solution

 

Two By Three Box
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    Keywords: Life & Death

1. No outside liberties

[Diagram]
Diag.: No outside liberties

If there are no outside liberties, White can kill Black unconditionally by playing at a.


[Diagram]
Diag.: Main line

After White 3, Black can't play at a because of damezumari. So, White can play there (or to the left of it) to capture the black stones (which she actually doesn't have to execute).



2. One outside liberty

[Diagram]
Diag.: One outside liberty

When there is exactly one outside liberty, the best White can do is to make it a (two stage) ko. The vital point is at a.


[Diagram]
Diag.: Main line

Black's throw in at 4 is necessary: if White gets to play there she makes it a bent four in the corner. White 5 starts the ko. White can "finish" this ko by connecting at 4. Black captures four stones at a setting up another ko (see next diagram).


[Diagram]
Diag.: Continuation

After the marked stone (Black a in the previous diagram), White sets up another ko with 1 and 3. She can finish the ko by connecting at 2, creating a bent three nakade. So, White has to win the ko two times to kill the corner and Black only once to live. [1]


[Diagram]
Diag.: White's failure

With one outside liberty, this White 1 fails. Black can play 4 because now he is not in atari.



3. Two or more outside liberties

[Diagram]
Diag.: Two outside liberties

When there are at least two outside liberties, Black is unconditionally alive.


[Diagram]
Diag.: Main line

The sequence is copied from the main line in the previous paragraph. Only now Black can play the surprising move of 6 because he still has at least two liberties. White cannot connect at 4 so Black will play there to make two eyes.



Addendum

In this diagram, Black is dead.

No, this is not a seki. Why?

[Diagram]
Diag.: Explanation 1

After White 1 and 3 fill up all the external liberties, the marked black stones are caught in a connect-and-die.


[Diagram]
Diag.: Explanation 2

If Black 1 prevents the connect-and-die at any point of the game, he turns his group into a straight three big eye instead and dies in gote.



Footnote:

[1]: One could argue that, this being the case, White might as well fill the outside liberty in the main line diagram instead of connecting at 4 there, but then Black is the first to capture the second stage of the ko and here it is White.


Authors:

WikiMasterEdited by Dieter. Original posts now at TwoByThreeBoxDiscussion.



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