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3-3 Invasion in 4-4+enclosure, trick move
http://www.lifein19x19.com/viewtopic.php?f=12&t=13536
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Author:  splittingfield [ Tue Aug 30, 2016 9:56 pm ]
Post subject:  3-3 Invasion in 4-4+enclosure, trick move

Hi,

I have a question concerning this kind of invasion:

Click Here To Show Diagram Code
[go]$$c invasion
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . W . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


Normally white now makes a ko. But recently I had this played against me, which josekipedia refers to as "trick play" without further comment:

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . W X . . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


I don't know how to play here as black. Everything I tried ends with white living directly or being able to cut black, which is a problem if black is not strong in the vicinity.

Author:  lodestone [ Tue Aug 30, 2016 10:50 pm ]
Post subject:  Re: 3-3 Invasion in 4-4+enclosure, trick move

It seems like black's C5 move might better be at B5.

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . B . . . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


But in your continuation, doesn't B6 A4 B2 kill?

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . X X . . . . . . .
$$ | . O X . . . . . . .
$$ | O . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . B . . . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


Or if W doesn't make a tiger's mouth, there's still a ko.

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . X X . . . . . . .
$$ | 6 O X . . . . . . .
$$ | . O O X . . . . . ,
$$ | 4 . O X . . . . . .
$$ | 7 2 3 1 . . . . . .
$$ | . 5 . . . . . . . .
$$ ---------------------[/go]

Author:  splittingfield [ Wed Aug 31, 2016 12:10 am ]
Post subject:  Re: 3-3 Invasion in 4-4+enclosure, trick move

I thought that white first hanes at the other side

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . 1 X . . . . . . .
$$ | . O X . . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . . 4 2 3 . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


Now black has to worry about the cut at E3 if he is not strong around. And if black fixes the cut white lives at B4.

Author:  Uberdude [ Wed Aug 31, 2016 12:36 am ]
Post subject:  Re: 3-3 Invasion in 4-4+enclosure, trick move

First to answer the original question, just block is correct. That exchange is white's right, but doesn't really help the corner live so it will likely still be the same ko as if white didn't make that exchange, and that exchange is a slight loss for white (it makes black stronger on the outside and increase his influence on the left side).

Click Here To Show Diagram Code
[go]$$Wc "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . 2 X . . . . . . .
$$ | . 1 X . . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


The continuation splittingfield worries about is indeed more likely for white, but it's locally dead with the bad aji of the cut, the same as without the bad exchange. White can then try a or b. The cut of a doesn't quite capture anything yet, whilst b clamp might escape with a 2nd line crawl that's usually worse than death.

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . 1 X . . . . . . .
$$ | 7 O X . . . . . . .
$$ | . 5 O X . . . . . ,
$$ | . 6 O X a . . . . .
$$ | . . 4 2 3 b . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


Note that in these variations white's hane-block exchange is a bad exchange as they made black stronger and with more eyeshape than without:

Click Here To Show Diagram Code
[go]$$Wc normal
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . 6 X . . . . . . .
$$ | . 4 O X . . . . . ,
$$ | . 5 O X . . . . . .
$$ | . . 3 1 2 7 . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


And now to correct lodestone's comments:

lodestone wrote:
It seems like black's C5 move might better be at B5.

Probably not unless the outside is special. White can live small like this:
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . B 2 . . . . . . .
$$ | . 1 O X . . . . . ,
$$ | 5 . O X . . . . . .
$$ | . 3 . 4 . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]

Or start the ko and black's outside is super weak (at a) if white wins it
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . B . a . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . 3 . 1 2 . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]

Or play somewhat heavier and just try living:
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . B . 6 . . . . . .
$$ | . 5 O X . . . . . ,
$$ | . . O X . 4 . . . .
$$ | 7 . 3 1 2 . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]

or if black extends then clamp either gets a in sente to live or escapes on 2nd line:
Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . B . 4 . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . . 3 1 2 5 . . . .
$$ | . . . a . . . . . .
$$ ---------------------[/go]


lodestone wrote:
But in your continuation, doesn't B6 A4 B2 kill?

Maybe, but with very bad aji. The much better way to kill is:
Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . X X . . . . . . .
$$ | . O X . . . . . . .
$$ | O 4 O X . . . . . ,
$$ | 6 3 O X . . . . . .
$$ | . 2 1 . 7 . . . . .
$$ | . 5 . . . . . . . .
$$ ---------------------[/go]


lodestone wrote:
Or if W doesn't make a tiger's mouth, there's still a ko.

No, dead:
Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . X X . . . . . . .
$$ | 7 O X . . . . . . .
$$ | 8 O O X . . . . . ,
$$ | 3 . O X . . . . . .
$$ | 9 2 4 1 . . . . . .
$$ | . 6 5 . . . . . . .
$$ ---------------------[/go]

Author:  splittingfield [ Wed Aug 31, 2016 4:49 am ]
Post subject:  Re: 3-3 Invasion in 4-4+enclosure, trick move

Thanks for your answer, I am more than satisfied! :bow:

Author:  dhu163 [ Thu Sep 01, 2016 5:55 am ]
Post subject:  Re: 3-3 Invasion in 4-4+enclosure, trick move

actually I think often a bigger reason is that after black plays the key point at D2, it becomes a flower ko for b (comparatively).

So often its not so much a trick play as a mistake, but it depends on the outside

Click Here To Show Diagram Code
[go]$$c "unconditional death"
$$ | . . . . . . . . . .
$$ | . 3 . . . . . . . .
$$ | . 2 X . . . . . . .
$$ | . O X . . . . . . .
$$ | 4 . O X . . . . . ,
$$ | . 5 O X . . . . . .
$$ | . . . 1 . . . . . .
$$ | . . . . . . . . . .
$$ ---------------------[/go]


Click Here To Show Diagram Code
[go]$$c "depends on outside"
$$ | . . . . . . . . . .
$$ | . 3 0 . . . . . . .
$$ | 5 2 X . . . . . . .
$$ | . O X . . . . . . .
$$ | 6 . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | 9 . 4 1 . . . . . .
$$ | . 8 7 . . . . . . .
$$ ---------------------[/go]

locally this is unconditional death, but the C7 cut is severe - B needs to be able to play A7 and A6 in response to B3 and A3

Click Here To Show Diagram Code
[go]$$c "bad ko"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . 3 X . . . . . . .
$$ | 4 O X . . . . . . .
$$ | . . O X . . . . . ,
$$ | 5 . O X . . . . . .
$$ | 6 7 2 1 . . . . . .
$$ | 9 8 . . . . . . . .
$$ ---------------------[/go]


if B loses the ko, it looks like this

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . X X . . . . . . .
$$ | O O X . . . . . . .
$$ | . . O X . . . . . ,
$$ | X O O X . . . . . .
$$ | O . O X . . . . . .
$$ | . O O . . . . . . .
$$ ---------------------[/go]


If B loses the ko in the normal variation in looks like this

Click Here To Show Diagram Code
[go]$$c "trick play"
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . X . . . . . . .
$$ | . . X . . . . . . .
$$ | . . O X . . . . . ,
$$ | . . O X . . . . . .
$$ | . O . O X . . . . .
$$ | . . O . O . . . . .
$$ ---------------------[/go]


B's shape is more broken

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