A gift for Willemien

[HermanHiddema]

For your corner shapes collection

Also for others of course, as a reading exercise...

$$W Status?
$$ -------------
$$ - . . X O O .
$$ - . . X X O .
$$ - . . . X O .
$$ - . . X X O .
$$ - X X X O . .
$$ - O O O . O .
$$ - . . . . . .

Click Here To Show Diagram Code

[go]$$W Status?
$$ -------------
$$ - . . X O O .
$$ - . . X X O .
$$ - . . . X O .
$$ - . . X X O .
$$ - X X X O . .
$$ - O O O . O .
$$ - . . . . . .[/go]

Additional question: does the status depend on the number of outside liberties? If so, how?

[gonut]

Did you know that in the old days, 20% of go players could solve 80% of tsumego problems? But nowadays, just the opposite is true. ...ahem... (Yes, my statistician jokes are even worse than my go ability.)

Anyway, with no outside liberties:

(;SZ[11]AB[ca][cb][db][dd][dc][cd][ce][be][ae]AW[af][bf][cf][de][ef][ed][ec][eb][ea][da]C[Status?]
;W[bc]C[Duh.]
(;B[ab];W[bb];B[ac];W[ba]C[White has a gote seki.])
(;B[bb]C[Might also work, depending on the global board situation.];W[ab];B[ad];W[ac]C[1000 year ko]))

And with an outside liberty:

(;SZ[11]AB[ca][cb][db][dd][dc][cd][ce][be][ae]AW[af][bf][cf][de][ef][ed][ec][eb][ea]C[Status? (Black has an outside liberty.)]
;W[bc];B[bb];W[ab];B[ac];W[ad];B[bd];W[da];B[aa]C[Black is alive in double ko, AND makes territory.])

[HermanHiddema]

Well, gonut got it completely right

Addition:

With at least two outside liberties, one of which can be an approach liberty, black can live without requiring double ko, which is better, because it doesn't give white unlimited ko threats.

The four main variations:

http://www.lifein19x19.com/forum/download/file.php?id=618