Here's a problem from my lunch-time game on KGS. White has just played , how should black kill? (Is it even possible to kill?)

Click Here To Show Diagram Code

[go]$$Wc Black to Respond
$$ | O X X X O . X . O O O X . X X X O . . |
$$ | X . X . X X X O O X X X O O X O . . . |
$$ | . . . X . . . X O O . X X O O . O . . |
$$ | . . . . . . . . X X . X O O O O . . . |
$$ | . . . X . . . X . , X . X X O X O O . |
$$ | . . . X . . . . X X O O X X X X X O . |
$$ | . . . . . . . X O O . . O 1 . . . X O |
$$ | . . . . . . . . . . . . . . . . . X . |
$$ +---------------------------------------+[/go]

In the game, I managed to kill white's invasion. When I went over the game, afterwards, I realised that I should have stopped it entirely, several moves earlier. I also realised that white could have lived and possibly cut off my lower-right group. In fact, I couldn't find a move for black that would prevent white from doing so.

EDIT: Also, have a look at this tsumego: http://eidogo.com/?game=1Lc8jeHa#1Lc8jeHa. The situation is similar, but black can live.

What if white plays 3 at 6?

4 at 5 works, right?

It's hard for me to prove.



There are a lot of variations from here. And maybe 5 (or 6) wasn't correct anyway.

Edit: After looking at this some more, I think white is still dead.

B looks fine to me, but I must be misreading horribly since I can't even see where the ko you mention would come from.

Click Here To Show Diagram Code

[go]$$Bc
$$ | O X X X O . X . O O O X . X X X O . . |
$$ | X . X . X X X O O X X X O O X O . . . |
$$ | . . . X . . . X O O . X X O O . O . . |
$$ | . . . . . . . . X X . X O O O O . . . |
$$ | . . . X . . . X . , X O X X O X O O . |
$$ | . . . X . . . . X X O O X X X X X O 8 |
$$ | . . . . . . . X O O . O O O X 6 4 X O |
$$ | . . . . . . . 3 9 2 X X . O 1 7 5 X . |
$$ +---------------------------------------+[/go]

Click Here To Show Diagram Code

[go]$$Bc
$$ | O X X X O . X . O O O X . X X X O . . |
$$ | X . X . X X X O O X X X O O X O . . . |
$$ | . . . X . . . X O O . X X O O . O . . |
$$ | . . . . . . . . X X . X O O O O . . . |
$$ | . . . X . . . X . , X O X X O X O O . |
$$ | . . . X . . . . X X O O X X X X X O . |
$$ | . . . . . . . X O O 8 O O O X 6 4 X O |
$$ | . . . . . . . 3 2 0 X X 9 O 1 7 5 X . |
$$ +---------------------------------------+[/go]

Four libs to three after W captures, no?

That's hard to read though. This is simpler:

Click Here To Show Diagram Code

[go]$$Wc
$$ | O X X X O . X . O O O X . X X X O . . |
$$ | X . X . X X X O O X X X O O X O . . . |
$$ | . . . X . . . X O O . X X O O . O . . |
$$ | . . . . . . . . X X . X O O O O . . . |
$$ | . . . X . . . X . , X 7 X X O X O O . |
$$ | . . . X . . . . X X O O X X X X X O . |
$$ | . . . . . . . X O O 8 5 O 1 2 . . X O |
$$ | . . . . . . . . . . 6 4 . 3 . . . X . |
$$ +---------------------------------------+[/go]

White has only two liberties and can't do a thing about it.

_________________
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Each of us woke up one moment and here we were in the darkness.
We're nameless things with no memory; no knowledge of what went before,
No understanding of what is now, no knowledge of what will be.

The ko came from me overthinking the problem Somewhere in the middle of the sequence I was playing w H1 and then b G1. Obviously b would play G2 though.

I guess the best white can do is take sente to play somewhere else, and then later come back and get a ton of ko threats out of the position by threatening to live.