Life In 19x19

Hello i stubled on this position that i christianed as a Stair ten in the corner

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[go]$$B
$$ --------------
$$ | . . . . X O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

I think that White can get a seki or a ko

But is there a way for Black to keep his territory?

PS this is in preperation for a page on sensei's library on this corner shape

I don't think that there is much long term benefit to doing this ( sorry! ), for arriving at the position almost certainly requires some serious DDK mistakes.

If the position gets to this point, such that black is getting locked in and running out of external liberties, 'a' is the natural play before 'b' or 'c'.

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[go]$$B
$$ --------------
$$ | . . . . b O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | c X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

willemien wrote:Hello i stubled on this position that i christianed as a Stair ten in the corner

$$B
$$ --------------
$$ | . . . . X O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$ --------------
$$ | . . . . X O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

I think that White can get a seki or a ko

But is there a way for Black to keep his territory?

PS this is in preperation for a page on sensei's library on this corner shape

White can get nothing here, it's just black territory.

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[go]$$W
$$ --------------
$$ | . 3 2 . X O .
$$ | 5 1 . X X O .
$$ | 4 6 X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

Click Here To Show Diagram Code

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

Click Here To Show Diagram Code

[go]$$W
$$ --------------
$$ | . 3 2 . X O .
$$ | 6 1 . X X O .
$$ | 4 5 X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

All other variations revert to one of these.

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[go]$$W
$$ --------------
$$ | . . 2 . X O .
$$ | . 1 . X X O .
$$ | 3 . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

Click Here To Show Diagram Code

[go]$$W
$$ --------------
$$ | . 4 2 . X O .
$$ | 7 1 5 X X O .
$$ | 3 6 X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

looks a lot like seki to me.
black can also start a ko with & , but this is a very bad ko for black.

Or a seki like this:

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[go]$$W
$$ --------------
$$ | . 5 2 . X O .
$$ | 7 1 4 X X O .
$$ | 3 6 X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

willemien wrote:Hello i stubled on this position that i christianed as a Stair ten in the corner

$$B
$$ --------------
$$ | . . . . X O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$ --------------
$$ | . . . . X O .
$$ | . a . X X O .
$$ | . . X X O . .
$$ | . X X O . O .
$$ | X X O . . . .
$$ | O O . O . . .
$$ | . . . . . . .[/go]

I think that White can get a seki or a ko

But is there a way for Black to keep his territory?

PS this is in preperation for a page on sensei's library on this corner shape

I would make problems out of this, it is such a special and unlikely shape to put to the corner shapes. And is it really a staircase, it looks suspiciously like a absent big b2 bomber to my eye

Heh, sorry, seems I posted to hastily. Seki indeed

I agree with tapir that it's not really suitable for corner shapes though, it is too uncommon and will just clutter the page, better as a tsumego.

HermanHiddema wrote:Heh, sorry, seems I posted to hastily...

A few more oversights and you'll be down to my level of accuracy.

thanks for all the answers.

I think it is a good shape for the Corner shapes page.

I always intended that page as a collection of different corner shapes that are just not territory.

and this is a rather simple ahape ( no cutting points or so)
and also it is one of the biggest shapes that is still not territory.

(or are there 11 point empty spaces without cutting points that can be turned into seki or ko?)

Another problem that is still bothering me what is the status of the [sl=]FiveStonesOnTheThirdLineInTheCorner[/sl]

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

willemien wrote:Another problem that is still bothering me what is the status of the [sl=]FiveStonesOnTheThirdLineInTheCorner[/sl]

$$B status?
$$+-------------------
$$|. . . . . . . . .
$$|. . . . . . . . .
$$|O O O O O X . . .
$$|X X X X X X . . .
$$|. . . . . . . . .

Click Here To Show Diagram Code

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

Depends who goes first.

Black can prevent easy life if he plays first:

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[go]$$B
$$+-------------------
$$|. 5 . 3 4 . . . .
$$|. . . . 2 1 . . .
$$|O O O O O X . . .
$$|X X X X X X . . .
$$|. . . . . . . . .[/go]

White can choose a ko:

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

..or a seki:

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

The ko is expensive for white and cheap for black. Also, white must win it several times. So white almost certainly prefers the seki.

Joaz Banbeck wrote:Black can prevent easy life if he plays first.

I don't think so:

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[go]$$B
$$+-------------------
$$|. 2 . . . . . . .
$$|. . . . . 1 . . .
$$|O O O O O X . . .
$$|X X X X X X . . .
$$|. . . . . . . . .[/go]

Seems I posted hastily too...

Joaz Banbeck wrote::oops:
Seems I posted hastily too...

Who is the other person who posted hastily? If it was me, rest assured I didn't and still stand by what I said as I was not thinking of in your figures:

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[go]$$Bc
$$+-------------------
$$|. 1 . . . . . . .
$$|. . . . . . . . .
$$|O O O O O X . . .
$$|X X X X X X . . .
$$|. . . . . . . . .[/go]

I am fairly certain that if it's Black to play and he plays first here, there is no way for White to live unconditionally. I would be delighted to see a refutation though as I couldn't find any after quite some thought. Instead of posting 8,318 different variations that seem to work, I'll just wait for variations from others that show White can live unconditionally and try to debunk those.