In the following diagram, the typical joseki would put B5 at a. Presumably that is because B5 is bad, but I am unable to give a good reason. Is it because B5 would essentially put black into being "haned at the head of two stones"?
I understand that go is very specific. In fact, in a slightly different setting, Kogo's joseki dictionary lists the following as possible exchange against Chinese opening:
B6 is somewhat similar, though there are also important differences.
Why would a bad move in first diagram would become acceptable in second diagram? Is it because W5 is going to be captured, and thus "hane at the head of two stone" is no longer applicable here?
Why this play is bad
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EdLee
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Hi GoStudent, yes, in this case, it is one reasongostudent wrote:Is it because B5 would essentially put black into being "haned at the head of two stones"?
is bad.In this variation: B would not want to put a stone at (x).
Kogo's has lots of errors. Just saying.
Also, FYI, BTW, the avalanches are an exception to "hane head of 2".
You're right about Go being very specific!
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Uberdude
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Re: Why this play is bad
White should extend like this.
Black helps white make strong connected 4th line territory (which is bad unless you get something awesome in return, which he doesn't here).
Last edited by Uberdude on Sun Dec 21, 2014 9:00 am, edited 2 times in total.
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Joaz Banbeck
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Re: Why this play is bad
Almost.gostudent wrote: ...Why would a bad move in first diagram would become acceptable in second diagram? Is it because W5 is going to be captured, and thus "hane at the head of two stone" is no longer applicable here?
The hane at the head of two stones is strong for at least two reasons:
1) It prevents the other player from continuing in a line. ( When both players have started a line of two stones, we can generally infer that both would like to continue that line to three or more. Thus preventing the other player from doing so with a hane is useful. )
2) It starts an encircling sequence, which can be lethal very quickly if the attacker gets the hane at the 'tail' also.
As shown, the hane still has force, and is still good for white. But when black has the tail of his two stones covered, the first part applies but the second does not.
But go players are vague. It provides a harmonious balance.gostudent wrote: I understand that go is very specific...
Help make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207
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Uberdude
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Re: Why this play is bad
As for the second question, of why bumping our head into hane-at-head of two shape is acceptable in the 2nd diagram, that is a rather more complicated, non-beginner question. First of all we need to understand why white made the crosscut of 5, and what would happen if he didn't but simply pulled back (also a good move):
The playing into hane-at-head-of-two that is analogous to the first diagram in the chinese variation would be doing it now (which is also bad, in fact probably worse):
So when white plays the crosscut, what is he aiming at that means simply capturing it is not so good?
So why does black play into hane-at-head-of-two instead? (there are other options too)
The meta-answer as to why bumping into hane-at-head is ok in your second diagram is because the crosscut means there is a complex tactical fight going on, so you can't just follow simple principles but need to read and play what works, even if it goes against some simple "bad shape" principle.
The playing into hane-at-head-of-two that is analogous to the first diagram in the chinese variation would be doing it now (which is also bad, in fact probably worse):
So when white plays the crosscut, what is he aiming at that means simply capturing it is not so good?
So why does black play into hane-at-head-of-two instead? (there are other options too)
The meta-answer as to why bumping into hane-at-head is ok in your second diagram is because the crosscut means there is a complex tactical fight going on, so you can't just follow simple principles but need to read and play what works, even if it goes against some simple "bad shape" principle.
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Bill Spight
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Re: Why this play is bad
At one time 
- 
was proposed as an answer to the Chinese opening. Two main variations were considered.
In the first variation, if Black is tempted to go after the
stone, 
- 
splits the Black formation in two, leaving a broken shape for Black. ("Broken shape" was not a term in use at that time.)
Black can prevent the broken shape by capturing this stone. But then - 
leaves Black overconcentrated.
counters both of those variations. It is why - is not played much today, if at all.
- was proposed as an answer to the Chinese opening. Two main variations were considered.In the first variation, if Black is tempted to go after the
stone, - splits the Black formation in two, leaving a broken shape for Black. ("Broken shape" was not a term in use at that time.)Black can prevent the broken shape by capturing this
stone. But then - leaves Black overconcentrated. counters both of those variations. It is why - is not played much today, if at all. The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Uberdude
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Re: Why this play is bad
@Bill, allowing the split and fighting a huge ko was pretty popular a year or two ago, I haven't seen it so much recently (whether that's just fashion or they decided it's good for someone I don't know, or maybe I'm just not looking at the games it still happens in). In fact white preferred the more powerful atari here, the simple connection is slack so play went like this.
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Re: Why this play is bad
@OP: You can compare the result to a normal joseki.
Normal (or extending 8 to be further).
vs.
Proposed The territory white gets around the corner makes me cringe as black, so it feels black is just giving away points to white. What did he get in exchange? I guess a tiger's mouth shape - the group is stable. But in the joseki, black's group is also stable, and doesn't give white free points.
It seems as simple as that - the proposed variation gives white points, and doesn't pressure white at all.
Normal (or extending 8 to be further).
vs.
Proposed The territory white gets around the corner makes me cringe as black, so it feels black is just giving away points to white. What did he get in exchange? I guess a tiger's mouth shape - the group is stable. But in the joseki, black's group is also stable, and doesn't give white free points.
It seems as simple as that - the proposed variation gives white points, and doesn't pressure white at all.
be immersed
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Kirby
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Re: Why this play is bad
As I understand it, this is a common variation these days: White lives in the corner, and gets sente. It should be an even result, as I understand.Bill Spight wrote:
If we consider the same line of thinking, just living in the corner would also seem similar with the given refutation.
Black could block at 'a', but white could perhaps counter with 'b' next.
Or perhaps white can try for more with something like this: Seems OK for white to me, given that the sequence above with white living in the corner is in fashion.
be immersed
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Bill Spight
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Re: Why this play is bad
First, the existence of 
means that this is not analogous to hane at the head of two stones.
In this position, would White play, hane at the head of two stones?
If we did start from a hane at the head position, would Black play
? White would be happy if he did.
As for
in the original diagram,
In this position would Black play? Puleaze!
means that this is not analogous to hane at the head of two stones.In this position, would White play
, hane at the head of two stones?If we did start from a hane at the head position, would Black play
? White would be happy if he did. As for
in the original diagram,In this position would Black play
? Puleaze!The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Bill Spight
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Re: Why this play is bad
@ Uberdude and Kirby
Thanks. Obviously I don't keep up. 
I wrote:
- was not played for 40 years.
Thanks.
Obviously I don't keep up. I wrote:
I should have said, That's whyBill Spight wrote:
- was not played for 40 years.The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Kirby
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Re: Why this play is bad
I attended the US Go Congress this last year in New York. It was a good experience, and we had the honor of having Park Jungsang 9p attend to give lectures, commentary, and game reviews. Kim Myungwan selected Park Jungsang 9p to attend, partly because of his up-to-date knowledge of pro trends, and his go knowledge in general. He's an active commentator on BadukTV, so he stays on top of go trends and fashions.Bill Spight wrote:@ Uberdude and Kirby
Thanks.
While he was there in New York, though it was only a week, he kept checking his smartphone for new developments. He said that, in the week that he was attending Go Congress, he was already falling behind with the latest trends. I was amazed that, even in the course of a week, he'd have cause for concern. He said that in that one week, his knowledge was becoming obsolete.
Go theory changes so quickly these days - even for 9d pros!
be immersed
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Bill Spight
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Re: Why this play is bad
Thanks.Uberdude wrote:@Bill, allowing the split and fighting a huge ko was pretty popular a year or two ago, I haven't seen it so much recently (whether that's just fashion or they decided it's good for someone I don't know, or maybe I'm just not looking at the games it still happens in). In fact white preferred the more powerful atari here, the simple connection is slack so play went like this.
The magazine article I recall was from the early 1970s. The author -- and presumably the editors -- regarded the broken shape as a sufficient refutation, despite the ponnuki in the corner. I guess that today's players do not. I was 2 kyu or shodan at the time, and accepted the author's opinion. It still seems like a sufficient refutation to me, but I am more concerned about the ponnuki than I was back then. One lesson here, I think, is to take joseki cum grano salis. Styles and opinions change over time. Joseki go out of favor and are resurrected. In the end, you have to develop your own judgement.
Joseki must stand the test of time. Here is one that did so. It appears in a game record from 196 A.D., and is still joseki. However,
fell out of favor in the 20th century. Oh, well. {shrug}Last night I was looking over a number of variations in defense against the Mini-Chinese. In the Igo Myoden, by Gennan Inseki, published in 1852.
That one made a comeback, eh? The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Bill Spight
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Re: Why this play is bad
Look again. The last diagram is significantly different from the previous one.Kirby wrote:As I understand it, this is a common variation these days: White lives in the corner, and gets sente. It should be an even result, as I understand.
If we consider the same line of thinking, just living in the corner would also seem similar with the given refutation.
Black could block at 'a', but white could perhaps counter with 'b' next.
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
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Bill Spight
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Re: Why this play is bad
Yes, it is quite an exciting time for joseki and fuseki research. Old dogmas are being questioned and overturned at a fairly rapid rate. My impression is that Korea is at the center of most of that.Kirby wrote:Go theory changes so quickly these days - even for 9d pros!
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.
At some point, doesn't thinking have to go on?
— Winona Adkins
Visualize whirled peas.
Everything with love. Stay safe.