Butterfly

    Keywords: Go term

Chinese: -
Japanese: - 觀音ビラキ (kannon-biraki)
Korean: -

[Diagram]
The butterfly  

The butterfly[1] formation results from making not one, but two large knight's moves from the corner starpoint. It is generally considered to be inefficient, since as it stands the 3-3 point invasion succeeds, while its two wings don't radiate as much power as wider enclosures would.

This shape is referred to as Kannon-biraki in Japanese. Kannon is the Japanese name of the Buddhist goddess of mercy (Skt. Avalokiteshvara). In everyday speech, Kannon-biraki refers to a type of double (or "French") door, originally used in cabinets containing images of the goddess.

A duller name would be 374473 enclosure. This is one of a number of unusual three-stone enclosures that are being seen more frequently in pro games.


Table of contents Table of diagrams
The butterfly
3-3 invasion becomes ko
3-3 invasion alternative
White still lives
White still lives
3-3 invasion alternative
3-3 invasion alternative
Other invasions
Orthodox
How to deal with this situation?
Black killing attempt
3-3 invasion alternative 2
Alive?
Still a ko?
Yet Another Way
Yet Another Way 2


3-3 point invasion

[Diagram]
3-3 invasion becomes ko  

This sequence occurred in a game of Dosaku (in 1678) and also in a game Yu Bin-Seo Pong-su in 2000. W11 at a, B12 at b, W13 at c sets up a ko; if White wins the ko the damage to Black's position will be serious, so this may almost be a picnic ko from White's point of view.

[Diagram]
3-3 invasion alternative  

If White really wants to avoid ko, she could play W13 here, in place of c, for unconditional life. B14 at W15 looks intimidating, but is an overplay.

[Diagram]
White still lives  

W15 is the answer. B16 is forced, whereupon W17 threatens bent three life, requiring B18. Now White unleashes W19, forcing B20 due to capture three to get an eye. After the cut of W21, Black is in pieces.

[Diagram]
White still lives  

Query part I: Following the previous sequence but without playing the eye-steal - This is still a better reduction than the second diagram isn't it?

[Diagram]
3-3 invasion alternative  

Query part II: Assuming the aji on the outside is just too much worse and the previous diagram ends up better, then I guess this is probably a fairly interesting continuation to have in the page (even if just for ko threats. As far as I can see, :w17: is required here for life, else it seems the vital point. If tenuki, then:

[Diagram]
3-3 invasion alternative  

This kills?


Other invasions

[Diagram]
Other invasions  

In practice, Black probably played at least one of the marked stones as a checking extension against a corresponding white stone. That makes the marked points interesting as possible invasions for White: if they connect out, a weak white group will gain in strength.


Alternatives

[Diagram]
Orthodox  

Black 1 here is the normal idea. The invasion point at a is then just some bad aji, not something White can use successfully at once.

Charles Matthews, Bob Myers

b in place of B1 is solid play.


Query

[Diagram]
How to deal with this situation?  

spindizzy1976 This is a situation which I have been caught in recently, where I tried to invade in a 2-stone handicap game. At first glance it looks like playing at a might give a ko, but actually maybe not? Anyway, I connected at b and ended up dying. Can anyone suggest what I should have done? Is it impossible to invade here?

kb: Playing at a gives a ko. It is probably your best option here - especially if Black is strong on the outside (Black has at least the marked stone supporting the butterfly formation). You can try to run but most likely you will be cut and die. If you are strong in the surrounding area, go ahead and run - punish your opponent for their overplay at B4.

[Diagram]
Black killing attempt  

If Black is strong on the outside, can he not play to kill instead of ko?


Another variation

What if Black plays B4 as shown here? How do we live unconditionally?

[Diagram]
3-3 invasion alternative 2  
[Diagram]
Alive?  

A and B miai for life.

[Diagram]
Still a ko?  
[Diagram]
Yet Another Way  
[Diagram]
Yet Another Way 2  

Looks like a two-step ko.

See also

BQM344


[1] Apparently a non-standard term coined by Charles Matthews.

Not. The term has been around for decades.


Butterfly last edited by 99.162.154.12 on November 1, 2016 - 19:17
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