Alter Igo Endgame Problems / Problem 1 Solution

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

Problem 1  

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

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.

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.

Solution 1b, moves 10-13  

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

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.)

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.

Analysis: collapsing seki. B8 elsewhere.  

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

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

Solution 1w (white first), moves 8-11  
Solution 1w (white first), moves 12-14  
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!

Alter Igo Endgame Problems / Problem 1 Solution last edited by on March 4, 2008 - 20:58
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