I would C11. B12 also works.

I would ignore it to play r18 and kill that entire top side white group

If white extends at s17 you play s18 to keep s17 down to only 2 liberties so you can capture it. Even if white plays first with the top group, once you've nabbed s17 it doesn't have enough space to live. Black m18 would capture 2 stones, but that's being kind to white as even if white plays m18 to save them for now, you play n19 to kill the entire white group (if you've already played r18).

Uberdude is right, OC.

Locally, the usual response to B-17 is C-17, which is not exactly obvious. It threatens D-18 to cut off and kill the two White stones in the corner. White usually replies at B-18 to save the stones.

OC, on any given board the right play may be different.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

To simplify the life and death problem, black to kill in the shape below:

Click Here To Show Diagram Code

[go]$$B
$$ --------------------------+
$$ . . . . . . . . . . . . . |
$$ . . X O O . . O O O X . . |
$$ . . X X X O O X X X X . . |
$$ . . . , . X X . . , . . . |
$$ . . . . . . . . . . . . . |[/go]

Now the game shape isn't quite the same as white can get a hane in sente. Can black still kill this?

Click Here To Show Diagram Code

[go]$$B
$$ --------------------------+
$$ . . . . . . . . . . O . . |
$$ . . X O O . . O O O X X . |
$$ . . X X X O O X X X X . . |
$$ . . . , . X X . . , . . . |
$$ . . . . . . . . . . . . . |[/go]

And can black still kill this?

Click Here To Show Diagram Code

[go]$$B
$$ --------------------------+
$$ . . . . . . . . . . O . . |
$$ . . X O O . . O O O X O . |
$$ . . X X X O O X X X X X . |
$$ . . . , . X X . . , . . . |
$$ . . . . . . . . . . . . . |[/go]

This should be fun, sloppy reading incoming

Correct pak0

Hi kythlyn, to improve we must work to get better at reading (among many other things ).