Alter Igo Endgame Problems / Problem 1 Solution
This is the solution to the Alter Igo endgame problem 1.
The question was, what is the best move for either color, and what is the result then.
is the vital point. is white's strongest resistance. Notice that will get removed as well.
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.
After black 11, white must fill an eye, so black captures at 13 and wins.
White should also begin with . Black must respond, or his stones will die in a collapsing seki. (Variations given below)
However, is a powerful tesuji. (In fact, it is so powerful that even the creator of the problem did not realize how powerful it was.)
Notice how 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.
White can force a mutual capture even if black has moves elsewhere.
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:
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!