my intuition is to take the ko, it seems urgent. If there wasnt any urgent situation, I would say top right is very big, so c15 would be my move.
So let me compare those: If I take the ko, white seems to have 3 options:
1. Try to fight the ko (most likely r14 as ko threat)
2. Say the ko is small and take a big move that is not a ko threat (I nominate c14 or at least that area)
3. Submit at g3
3 seems very bad and in that case it was definitely good to take the ko, so I`m going to discard. In case of 1, both answering at s14 and trying for mutual destruction at g3 seem plausible. I think I would be tempted to try g3, but for this argument I think it is enough to say, if I just answer the ko threat it was already a good idea to take the ko and make him spend that threat that also loses him a liberty.
So the variation I really have to look at is 2.
On the other hand, if black doesnt take the ko, but plays upper left, white is supposed to punish him by doing something in the lower left, so I should figure out what that is.
My variations:
Variation, black takes the ko
- Click Here To Show Diagram Code
[go]$$Bcm25 Variation, black takes the ko
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . O . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . 2 . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . . X X O X . . . . . . . . X . . . |
$$ | . . X , O 1 O X . , . . . . . , . . . |
$$ | . . . . O O 3 O . . . . . . . X . . . |
$$ | . . . . . . 4 . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Variation, white makes the ko big, black resists
- Click Here To Show Diagram Code
[go]$$Bcm25 Variation, white makes the ko big, black resists
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . O . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . 1 . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O 4 6 . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . . . 2 X . . . . . . . . . . . . . |
$$ | . . . X X O X . . . . . . . . X . . . |
$$ | . . X , O 3 O X . , . . . . . , . . . |
$$ | . . . . O O 5 O . . . . . . . X . . . |
$$ | . . . . . . 7 . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Variation, white defends the ko
- Click Here To Show Diagram Code
[go]$$Bcm25 Variation, white defends the ko
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . O . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . 1 . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O 5 . . . . . . . . . . . . . |
$$ | . . . . 3 X 4 . . . . . . . . . . . . |
$$ | . . . X X O X 6 . . . . . . . X . . . |
$$ | . . X , O 2 O X . , . . . . . , . . . |
$$ | . . . . O O . O . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
Actually I like all 3 variations for black...
In the first one, making wheite answer 28 seems like a success. As for the evaluation, upper left is about as good as lower right, upper right is a joseki with even number of stones, so I`ll call that even and lower left seems good for black given that its his move and he is nicely out. White is also not too bad though, he is fine on the bottom (black cant really start the ko again) and the 2 stones on the left are little funny, but work with the top left...
Variation 2 is terrible for white, because 26 is now a wasted move, so forget that.
Variation 3 Is again hard to judge. I call the top even, both corners even number of stones in reasonable places. On the bottom withe seems locally better in bottom left but does it make up for the bottom right. I dont really think so, black adds a move on the left(e8?, c10?) and he seems fine... Also I´m not sure about the whole variation altogether...
The variations seem very close and maybe even Indicate c15 was better, but my gut says take the ko and it feels really good to make white defend with 28 and probably once more if you connect, so I´ll go with that. dont know what white is supposed to do, if black doesnt take the ko though.
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Bill Spight
)
, 
, and 
are all errors, each losing more than 6% to par. 
plays the turn, allowing 
to capture the 
stone. Then 
approaches the top left corner.
stone is huge. This kind of sente ko arises frequently in the opening, though often closer to the edge, and it is almost always right to take it immediately. Note that Black's threat to capture 