Take the 2-minute tour ×
Board & Card Games Stack Exchange is a question and answer site for people who like playing board games, designing board games or modifying the rules of existing board games. It's 100% free, no registration required.

I know the following is joseki for an approach of the 4-4 stone followed by a 3/3 invasion...

$$cm1 A normal 3/3 invasion joseki (incomplete)
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 7 3 . . 2 . . . . . . . . . . . . . |
$$ | . 5 4 O . . . . . , . . . . . , . . . |
$$ | . 6 8 . . . . . . . . . . . . . . . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

.. and this is a possible continuation:

$$cm1 Continuation of the joseki
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . X X 1 2 O . . . . . . . . . . . . . |
$$ | . X O O . . . . . , . . . . . , . . . |
$$ | 4 O O . 6 . . . . . . . . . . . . . . |
$$ | . 3 X 5 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

If I understand correctly, a white move at E18 has to be answered by black, or white A16 kills. Eidogo lists only black 7 as above at this point. It does not list the following variation, hence, I assume it is somehow bad for black, but I am not sure why.

$$cm1 Deviation from joseki
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 3 1 2 . . . . . . . . . . . . . |
$$ | . X X X O O . . . . . . . . . . . . . |
$$ | . X O O . . . . . , . . . . . , . . . |
$$ | O O O . O . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
  • Am I correct that black is alive like that? If not, please show how to kill black.
  • Given that black is alive in both variants, why would one prefer the default variant? I first thought that 7 may be sente, but with E18 threatening to kill it seems gote just as well, while getting fewer points?

(I'm sorry if this is a duplicate question, but I have no idea how to search a stackexchange site for go-deviations really)

share|improve this question
    
I believe playing 3 at D19 in the deviation would let the corner live unconditionally. –  goldPseudo Jan 23 '12 at 2:26
    
We do not yet have a good way to search for specific positions or joseki sadly ;( Btw, I see this is your first question here (and already really well formatted!), so welcome on Board and Card Games :) –  mafutrct Jan 23 '12 at 12:03

1 Answer 1

up vote 6 down vote accepted

In the deviated form, white can play at B18 and the corner will live or die as a ko, or it can end up in seki. Even if black has more than enough ko threats to win the battle, it is unlikely ever worth it.

$$Wcm4 Continuation of deviation: Ko
$$ +---------------------------------------+
$$ | 7 . 3 6 5 . . . . . . . . . . . . . . |
$$ | 2 1 a X X O . . . . . . . . . . . . . |
$$ | . X X X O O . . . . . . . . . . . . . |
$$ | 4 X O O . . . . . , . . . . . , . . . |
$$ | O O O . O . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

The corner lives or dies depending on who wins the two stage ko; black's normal defense of playing 7 at a won't work due to a shortage of liberties.

Alternatively, if white does not have sufficient ko threats the whole corner could end up as a seki as follows:

$$Wcm4 Continuation of deviation: Seki
$$ +---------------------------------------+
$$ | 8 a 3 6 5 7 . . . . . . . . . . . . . |
$$ | 2 1 . X X O . . . . . . . . . . . . . |
$$ | . X X X O O . . . . . . . . . . . . . |
$$ | 4 X O O . . . . . , . . . . . , . . . |
$$ | O O O . O . . . . . . . . . . . . . . |
$$ | . X X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

Note that in this variation, black can choose to start the same ko by playing 11 at a instead.

share|improve this answer
    
In the first example, black 5 looks like a mistake. What happens if black responds at White 8? I see White C19, Black A16, White A18, Black B19, White A19, Black C18 for seki. White can still force a ko by playing A18 at A19, but now it's an approach ko for white. And no longer two step. –  OmnipotentEntity Jan 23 '12 at 22:41
    
@OmnipotentEntity: White avoids the approach ko with A16 instead of C19. I believe the best black can hope for there is a direct ko with white capturing first. –  goldPseudo Jan 23 '12 at 23:37
    
Well, you have my vote. :) –  OmnipotentEntity Jan 24 '12 at 2:04

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.