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What rank is this tsumego?

Posted: Thu Apr 07, 2022 9:06 am
by Cyan
I've been practising a lot of tsumego but missed this kill in a game. Wondering if I should be able to solve it (meaning I should learn to recognize tsumego in live games) or if it's above my rank?

Black to kill:

Image

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 11:58 am
by kvasir
Maybe it is a hard one?

I tend to divide tsumego into categories depending on if it is a "learning" problem or a "reading" problem. "Learning" problem is something you study, possibly memorize and try to learn something new. "Reading" problem is one that practices reading, because it is tricky or the solution is unexpected. My approach with "reading" problems is to never look at the solution, I'll try but I won't check if it is correct because I don't see that as the point of the exercise. Also if I am not sure I have the solution this is also a practical answer. As you improve some "reading" problems might change categories and become something to study.

If I am not missing something then I'd call this a "reading" problem and wouldn't try to memorize it.

I said I wouldn't look at the solution but that doesn't mean I wouldn't talk about it with anyone :) Are you sure black can kill?
Click Here To Show Diagram Code
[go]$$B ko?
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . . O O X . . . . . . |
$$ X . . . , . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . 3 4 . O O X . . . |
$$ O . . . 5 2 1 6 . 7 . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$B life?
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . . O O X . . . . . . |
$$ X . . . , . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . . 2 . O O X . . . |
$$ O . . . 6 3 1 4 . 5 . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$ dead but other white moves
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . 9 O O X . . . . . . |
$$ X . . . 8 . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . 4 3 . O O X . . . |
$$ O . . . 5 1 2 6 . 7 . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$ life?
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . . O O X . . . . . . |
$$ X . . . 6 . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X 5 3 4 . O O X . . . |
$$ O . . . 2 1 . . . . . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$ life?
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . . O O X . . . . . . |
$$ X . . . , . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X 3 5 6 . O O X . . . |
$$ O . . . 2 1 4 . . . . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$ life?
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . . O O X . . . . . . |
$$ X . . . . 5 . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . 2 1 . O O X . . . |
$$ O . . . 3 . . 4 . 6 . . . . |
$$ ----------------------------[/go]
Maybe I missed something.

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 12:11 pm
by Cyan
Seems like this is a hard reading problem, plus the time pressure and the whole board position in a live game makes it even harder. I think black can kill in this way, is this correct?
Click Here To Show Diagram Code
[go]$$ Solution 1
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . 9 O O X . . . . . . |
$$ X . . . 8 . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . 2 1 . O O X . . . |
$$ O . . . 3 5 4 6 . 7 . . . . |
$$ ----------------------------[/go]
Click Here To Show Diagram Code
[go]$$ Solution 2
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . 9 O O X . . . . . . |
$$ X . . . 8 7 . O X . , . . . |
$$ O X X X . O 6 O X . X . . . |
$$ . O O X . 2 1 . O O X . . . |
$$ O . . . 3 . . 4 . 5 . . . . |
$$ ----------------------------[/go]

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 12:31 pm
by kvasir
Yeah. That seems to check out.
Click Here To Show Diagram Code
[go]$$
$$ . O X . . X . . . . . . . . |
$$ . . X X X O X X . . . X . . |
$$ . X O . 7 O O X . . . . . . |
$$ X . . . 6 . . O X . , . . . |
$$ O X X X . O . O X . X . . . |
$$ . O O X . 2 1 . O O X . . . |
$$ O . . . 3 . . 4 . 5 . . . . |
$$ ----------------------------[/go]

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 12:37 pm
by Cyan
Thanks, I want to put this problem on a tsumego site, but I have no experience in making tsumego. How should I simplify this position into a tsumego?

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 12:42 pm
by Cassandra
Cyan wrote:I've been practising a lot of tsumego but missed this kill in a game. Wondering if I should be able to solve it (meaning I should learn to recognize tsumego in live games) or if it's above my rank?
It will make a decisive difference if you encounter this problem presented as a tsume-go, or in a real game.

If it is a tsume-go, you will be sure that there is a way for Black to kill White's group.
In my experience, this knowledge alone makes it easier in many cases to find the solution.

In a real game, there will still exist some kind of uncertainty, if you did not encounter the key-shapes and key-tesuji of this formation (probably often enough) before.

Thus said, this problem might have been above your rank in a real game, and below (or suitable for) your rank as a genuine tsume-go.

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 12:49 pm
by Cassandra
Cyan wrote:Thanks, I want to put this problem on a tsumego site, but I have no experience in making tsumego. How should I simplify this position into a tsumego?
This positiion is fine as a tsume-go, there is NO need for simplification.

But it would be necessary to identify the key points of shape, as well as some other relevant properties of the stones / strings involved.

Tomorrow at the latest, I will post here an example of my thinking in this regard.
Now it is very late in the evening and I still have to walk my two dogs (one of them is called HONTE :D ).

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 1:34 pm
by Cyan
I added this tsumego to 101weiqi, please take a look and give it a rating!

https://www.101weiqi.com/auditquestion/318584/

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 3:02 pm
by Knotwilg
I'm 2d. In a game I would surely go for the kill with :b1: as in the solution but I would probably screw up at :b3: because I'd try to falsify the upper eye next, giving White an opportunity to force life at the bottom.

In my practice blog here you will see my latest post featuring a fairly easy tesuji problem which however wasn't trivial for me in the real game. As someone else pointed out, knowing there *is* something, is probably worth a couple of ranks already.

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 9:45 pm
by weakwest
It's really easy. At most like a 5k 101weiqi problem? No offense but the posters finding it difficult probably have poor life and death skills

Re: What rank is this tsumego?

Posted: Thu Apr 07, 2022 11:04 pm
by Cassandra
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . . . . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
The space is very open, so the shape analysis is not that trivial.
Click Here To Show Diagram Code
[go]$$W
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . . 1 . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
If it was White's turn ...
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O C O X . X . . . |
$$ | . . . . . . O O X . . O C O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
White's group has two sure eyes.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O T O X . X . . . |
$$ | . . . . . . O O X . T T T O O X . . . |
$$ | . . . . . O . . . . . T T . . . . . . |
$$ +---------------------------------------+[/go]
A nakade shape inside White's formation.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O Z . . . X . . |
$$ | . . O , . X . . . , . M O X . , . . . |
$$ | . . . . O O X X X . O . O Z . X . . . |
$$ | . . . . . . O O X . . . M O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
Two cutting points.
Click Here To Show Diagram Code
[go]$$W
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X 3 X X . . . . . . |
$$ | . . . . . . X O . . 3 3 X . . . X . . |
$$ | . . O , . X . . . , . . 3 X . , . . . |
$$ | . . . . O O X X X . O . 3 X . X . . . |
$$ | . . . . . . O O X . . . . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
Two White strings with only three liberties.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . T O X . , . . . |
$$ | . . . . O O X X X . O T O X . X . . . |
$$ | . . . . . . O O X . . T . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
This makes one think about another nakade shape.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . . ? . 4 4 X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
White's string at the right has four liberties.
But which a Black stone at the shadowed point would have, too.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . M O O X . . . X . . |
$$ | . . O , . X . . . , M . O X . , . . . |
$$ | . . . . O O X X X M O . O X . X . . . |
$$ | . . . . . . O O X . . . . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
A potential false eye at the top.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . . 1 . O O X . . . |
$$ | . . . . . O . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]
:b1: is played at the apparent vital point of the problem.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X 7 X . . . |
$$ | . . . . . . O O X . 2 X 3 O O X . . . |
$$ | . . . . . O . . . . . 8 4 . 5 . . . . |
$$ +---------------------------------------+[/go]
Trial continuation at the right.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O O O X X X . . . |
$$ | . . . . . . O O X . O C C O O X . . . |
$$ | . . . . . O . . . . . O O . X . . . . |
$$ +---------------------------------------+[/go]
White got only one eye at the bottom.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . M O O X . . . X . . |
$$ | . . O , . X . . . , M . O X . , . . . |
$$ | . . . . O O X X X M O O O X X X . . . |
$$ | . . . . . . O O X . O . . O O X . . . |
$$ | . . . . . O . . . . . O O . X . . . . |
$$ +---------------------------------------+[/go]
At the top, there is still the potential false eye.
Click Here To Show Diagram Code
[go]$$Bm9
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 1 . O X . , . . . |
$$ | . . . . O O X X X . O O O X X X . . . |
$$ | . . . . . . O O X b O . . O O X . . . |
$$ | . . . . . O . . a 2 . O O . X . . . . |
$$ +---------------------------------------+[/go]
But :w10: makes miai of A and B.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . 2 1 . O O X . . . |
$$ | . . . . . O . . . 3 . . . . . . . . . |
$$ +---------------------------------------+[/go]
Therefore, Black must pre-empt White's life-creating move by playing a diagonal move to :b3: himself.

White is dead.

Re: What rank is this tsumego?

Posted: Sat Apr 09, 2022 7:30 am
by Gérard TAILLE
Knotwilg wrote:I'm 2d. In a game I would surely go for the kill with :b1: as in the solution but I would probably screw up at :b3: because I'd try to falsify the upper eye next, giving White an opportunity to force life at the bottom.
I do not see where you can play a wrong move:

The logical sequence seems the following
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 7 . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X . X . . . |
$$ | . . . . . . O O X . 2 1 3 O O X . . . |
$$ | . . . . . O . . . . . . 4 . 5 . . . . |
$$ +---------------------------------------+[/go]
and with your suggestion to falsify the upper eye the move :b7: kills white doesn't it?

BTW in the following position
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X c 2 1 d O O X . . . |
$$ | . . . . . O . . a b . . . . . . . . . |
$$ +---------------------------------------+[/go]
the moves a, b, c or d seem killing moves but in practice the move "a" is certainly the best one for a yose point of view.

Re: What rank is this tsumego?

Posted: Sat Apr 09, 2022 8:18 am
by Knotwilg
[quote="Gérard TAILLE"][/quote]

See previous answers. Your 4 is thé wrong hane. Then a diagonal decent nu white threatens to connect or make a 2nd eye

Re: What rank is this tsumego?

Posted: Sat Apr 09, 2022 8:24 am
by Cassandra
Gérard TAILLE wrote:
Knotwilg wrote:I'm 2d. In a game I would surely go for the kill with :b1: as in the solution but I would probably screw up at :b3: because I'd try to falsify the upper eye next, giving White an opportunity to force life at the bottom.
I do not see where you can play a wrong move:

The logical sequence seems the following
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 7 . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X . X . . . |
$$ | . . . . . . O O X . 2 1 3 O O X . . . |
$$ | . . . . . O . . . . . . 4 . 5 . . . . |
$$ +---------------------------------------+[/go]
and with your suggestion to falsify the upper eye the move :b7: kills white doesn't it?
Knotwilg was faster ;-)
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 7 . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X . X . . . |
$$ | . . . . . . O O X 0 O X X O O X . . . |
$$ | . . . . . O . . 9 8 . 4 . . 5 . . . . |
$$ +---------------------------------------+[/go]
:w4: must be played from the inside, NOT from the outside.

Re: What rank is this tsumego?

Posted: Sat Apr 09, 2022 9:51 am
by Gérard TAILLE
Cassandra wrote:
Gérard TAILLE wrote:
Knotwilg wrote:I'm 2d. In a game I would surely go for the kill with :b1: as in the solution but I would probably screw up at :b3: because I'd try to falsify the upper eye next, giving White an opportunity to force life at the bottom.
I do not see where you can play a wrong move:

The logical sequence seems the following
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 7 . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X . X . . . |
$$ | . . . . . . O O X . 2 1 3 O O X . . . |
$$ | . . . . . O . . . . . . 4 . 5 . . . . |
$$ +---------------------------------------+[/go]
and with your suggestion to falsify the upper eye the move :b7: kills white doesn't it?
Knotwilg was faster ;-)
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , 7 . O X . , . . . |
$$ | . . . . O O X X X . O 6 O X . X . . . |
$$ | . . . . . . O O X 0 O X X O O X . . . |
$$ | . . . . . O . . 9 8 . 4 . . 5 . . . . |
$$ +---------------------------------------+[/go]
:w4: must be played from the inside, NOT from the outside.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . 2 1 3 O O X . . . |
$$ | . . . . . O . . . . . . 4 a 5 . . . . |
$$ +---------------------------------------+[/go]
When white plays hane on the outside white threatens to make an eye at "a" and the answer :b5: is natural.
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ | . . . . . . . X X X O X X . . . . . . |
$$ | . . . . . . X O . . O O X . . . X . . |
$$ | . . O , . X . . . , . . O X . , . . . |
$$ | . . . . O O X X X . O . O X . X . . . |
$$ | . . . . . . O O X . 2 1 3 O O X . . . |
$$ | . . . . . O . . c 5 b 4 . . . . . . . |
$$ +---------------------------------------+[/go]
OC, similarly, when white plays hane on the inside white threatens to make an eye at "b" and the answer :b5: is still natural.
BTW, instead of :b5: it may be better for black to answer at "c".
I still do not see how white can live.