Alter Igo Endgame Problems / Problem 1 Solution

This is the solution to the Alter Igo endgame problem 1.

[Diagram]

Problem 1

The question was, what is the best move for either color, and what is the result then.


[Diagram]

Solution 1b (black first), moves 1-2

B1 is the vital point. W2 is white's strongest resistance. Notice that W2 will get removed as well.


[Diagram]

Solution 1b, moves 3-9 (W8 at B7)

White does not want to play at the upper left corner, because that would give black a fourth eye. So white persists on the right.

[Diagram]

Solution 1b, moves 10-13

After black 11, white must fill an eye, so black captures at 13 and wins.


[Diagram]

Solution 1w (white first), moves 1-2

White should also begin with W1. Black must respond, or his stones will die in a collapsing seki. (Variations given below)

However, B2 is a powerful tesuji. (In fact, it is so powerful that even the creator of the problem did not realize how powerful it was.)

[Diagram]

Analysis: collapsing seki. B2 elsewhere

Notice how B4 removes also the 2 black stones. Also note that a black play in the lower left corner would have self-captured black's main group too.

[Diagram]

Analysis: collapsing seki. B8 elsewhere.

White can force a mutual capture even if black has moves elsewhere.

[Diagram]

Solution 1w (white first), moves 3-5

[Diagram]

Solution 1w (white first), moves 6-7

Now it is important to notice, that black can always "waste a move" in the upper left corner, that is, he can play there, and end with sente and an eye. This enables black to kill:

[Diagram]

Solution 1w (white first), moves 8-11

[Diagram]

Solution 1w (white first), moves 12-14

[Diagram]

Solution 1w (white first), moves 15-18

So even if white plays first, black still wins because of his three-space eye with 2 prisoners inside. Not quite what I thought when I created this problem a couple of months back!


This is a copy of the living page "Alter Igo Endgame Problems / Problem 1 Solution" at Sensei's Library.
(OC) 2014 the Authors, published under the OpenContent License V1.0.
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