I didn't save the position, but I remember approximately how I got there.
If we start at this position:
$$Wc
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O . X O . . |
$$ | . O O X . . . O . O X O O X X X X X . |
$$ | . . O X . . X . O . X O X O O O O O . |
$$ | . . O X . . . . O X X O X X X X . . . |
$$ | . . O X . . . . O . X X O O X X O 5 . |
$$ | . X X O X . X . . O O O O X O X X 1 . |
$$ | . O O O . . . . . . . . . . O O 2 4 . |
$$ | . . . . . X . . . X . . . . . . 3 6 . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O . X O . . |
$$ | . O O X . . . O . O X O O X X X X X . |
$$ | . . O X . . X . O . X O X O O O O O . |
$$ | . . O X . . . . O X X O X X X X . . . |
$$ | . . O X . . . . O . X X O O X X O 5 . |
$$ | . X X O X . X . . O O O O X O X X 1 . |
$$ | . O O O . . . . . . . . . . O O 2 4 . |
$$ | . . . . . X . . . X . . . . . . 3 6 . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . . . . . . . . |
$$ | . . X . X . . . . . . . . . . . . . . |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
...which you can find in this post:
http://lifein19x19.com/forum/viewtopic. ... 723#p45723...we can end up at this position:
$$Wc 3 is forced, btw
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O . X O . . |
$$ | . O O X . . . O . O X O O X X X X X . |
$$ | . . O X . . X . O . X O X O O O O O a |
$$ | . . O X . . . . O X X O X X X X 3 . b |
$$ | . . O X . . . . O . X X O O X X O O . |
$$ | . X X O X . X . . O O O O X O X X O 2 |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X 8 |
$$ | . . . O . . . . . . . . . . . . 1 4 . |
$$ | . . . . . X . . . . . . . . . . . 5 6 |
$$ | . . X . X . . . . . . . . . . . . . 7 |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc 3 is forced, btw
$$ ---------------------------------------
$$ | . . . . . . . O . . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O . X O . . |
$$ | . O O X . . . O . O X O O X X X X X . |
$$ | . . O X . . X . O . X O X O O O O O a |
$$ | . . O X . . . . O X X O X X X X 3 . b |
$$ | . . O X . . . . O . X X O O X X O O . |
$$ | . X X O X . X . . O O O O X O X X O 2 |
$$ | . O O O . . . . . . . . . . O O X X . |
$$ | . . . . . X . . . X . . . . . . O X 8 |
$$ | . . . O . . . . . . . . . . . . 1 4 . |
$$ | . . . . . X . . . . . . . . . . . 5 6 |
$$ | . . X . X . . . . . . . . . . . . . 7 |
$$ | . . . , . O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
My memory is a bit fuzzy here. There may have been an exchange of 'a' for 'b'.
In some variations, after the a-b exchange, black is stymied from the top, but can approach from the bottom. To stall this, prior to black 8 white throws in at 'c' to make black's 'd' a self-atari.
$$Wc
$$ ---------------------------------------
$$ | . . . . . i . O j . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O f X O e . |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X O O O O O X |
$$ | . . O X . . . . O X X O X X X X O . O |
$$ | . g O X . . . . O . X X O O X X O O d |
$$ | . X X O X . X . . O O O O X O X X O X |
$$ | . O O O . . . . . . . . . . O O X X c |
$$ | . . . . . X . . . X . . . . . . O X 8 |
$$ | . . . O . . . . . . . . . . . . O X . |
$$ | . . . . . X . . . . . . . . . . . O X |
$$ | . . X . X . . . . . . . . . . . . . O |
$$ | . . . , h O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . . . . . i . O j . . . . . . . . . . |
$$ | . X X O O . O X . . . . . . . . . . . |
$$ | . X O O . O X X . . . X . . O X X . . |
$$ | . X X O O X O X . X X O X . O O X . . |
$$ | X X O X . X O O X O X . O O f X O e . |
$$ | . O O X . . . O . O X O O X X X X X X |
$$ | . . O X . . X . O . X O X O O O O O X |
$$ | . . O X . . . . O X X O X X X X O . O |
$$ | . g O X . . . . O . X X O O X X O O d |
$$ | . X X O X . X . . O O O O X O X X O X |
$$ | . O O O . . . . . . . . . . O O X X c |
$$ | . . . . . X . . . X . . . . . . O X 8 |
$$ | . . . O . . . . . . . . . . . . O X . |
$$ | . . . . . X . . . . . . . . . . . O X |
$$ | . . X . X . . . . . . . . . . . . . O |
$$ | . . . , h O . . . , . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
White has internal ko threats at 'e' and then 'f'. Black has only external ko threats. This advantage may be enough to allow white to defend the most dangerous threat at 'g', and force black to take the threat at 'h' or 'i'.
BTW, my previous note about a subsequent two-step ko up top was wrong. I was carelessly asuming that the ko theat against that group would be 'j', but 'i' is clearly better.