Countering mirror go

  Difficulty: Beginner   Keywords: Opening, Humour

Mirror go played by White can be countered by Black playing on the tengen, although this is not necessarily the best way. Below are several examples of countering mirror go. Of course, the result is often absurd, but if the player who is mimicking aborts halfway, the other player would have succeeded in stopping the mirror go.

blubb: This page mainly deals with techniques that can force the other player to stop mimicking. However, the more challenging task is to do so without giving your opponent any opportunity to take advantage of your mirror defense attempt (by suddenly responding with a better move than yours) [2].

Table of contents
Table of diagrams
Countering mirror go (1)
Countering mirror go (1)
Countering mirror go (1)
Countering mirror go (2)
Countering mirror go (2)
Countering mirror go (2)
Countering mirror go (2)
Countering mirror go (2)
How to counter mirror go there?
Countering central-group mirror go
counter mirroring by ring capture
the same, even closer to the center

DamienSullivan: This page is classified under Humour, but I think it's not just funny stuff; it would be interesting (and upsetting) if slavish mirroring always gave drawn games, or even boring losses, with interesting games only being because of an agreement to struggle. E.g. it's possible to have a rock-paper-scissors tournament, if the players are trying to find patterns in each other's guesses and exploit them, as opposed to using a stronger random play strategy. That mirroring can be soundly punished reassures me.

I'd also say that it seems the non-superko strategies have a common idea: entangling a group with its mirror, and being the first to give atari. If the atari is mirrored then you capture; if the mirror breaks off to escape then at least you've broken it, and hopefully can get them on the run. Defeating a mirror in normal handicap go might be different: capture a handicap stone, build a second eye, then have the group surrounded. The mirror group needn't be in contact, but will die because there's a handicap stone where one of its eyes should be.

1. Shortage of liberties due to tengen

The opponent stone at tengen can be used to create shortage of liberties.

[Diagram]

Countering mirror go (1)

[Diagram]

Countering mirror go (1)

[Diagram]

Countering mirror go (1)

[1]

What's the best continuation if B7 connects at 8?


2. Setting up two ladders

If no opponent stone at tengen is available to create shortage of liberties, then setting up two ladders is another technique.

[Diagram]

Countering mirror go (2)

[Diagram]

Countering mirror go (2)

[Diagram]

Countering mirror go (2)

[Diagram]

Countering mirror go (2)

[Diagram]

Countering mirror go (2)



--unkx80


3. Anomalies in handicap Go

How about this kind of 6-H mirror go ? (Assuming that rules allow Black to place handicap stones where he desires.)

[Diagram]

How to counter mirror go there?

Since there is no komi, the extra moku given by the tengen should give victory to Black. I see no obvious way to counter the symmetry. -- MrKoala

[Diagram]

Countering central-group mirror go

Here we see White beating the above-mentioned mirror go. White 1 captures 36 black stones, but Black 2 does not capture the corresponding white stones, because they have gained two liberties through White's capture - Andre Engels

Thanks a lot, Andre Engels. I think it could also be applied to the tengen-as-first-move mirror go, couldn't it ? -- MrKoala

SAS: There seems to be a practical problem with the method shown above for countering the 6-stone handicap mane-go. If Black stops mimicking as soon as White plays on the first line, then White's position is pretty bad --- even allowing for the 6-stone difference in stength I think it may be difficult for White to win in the face of Black's huge moyo.

This is the solution used in Hikaru no Go -- Avery

blubb: The capturing ring doesn't have to crawl along the border, it can also be settled somewhat closer to the center:

[Diagram]

counter mirroring by ring capture

[Diagram]

the same, even closer to the center



But, still, these situations are highly artificial.


4. A standard anti-mane-go strategy, setting up two kos

Here's another standard anti-mane-go strategy that can be used instead. It assumes that some form of superko rule is in force. White starts by creating two kos; call these kos A and B, and their mirror images A' and B'. White captures in A, and Black mimics by capturing in A'. Then White captures in B, and Black captures in B'. Then White recaptures in A', and Black recaptures in A. Then White recaptures in B'. The superko rule forbids Black from recapturing in B, so he has to stop mimicking.

blubb: Nice! This sounds much more likely to be usable. It's not too hard to set up a few big kos, even without providing "weak" moves which could make the opponent stop mirroring.


[1] The Countering (1) example looks to be Akira's game against Okamura in Hikaru no Go chapters 14-15. --TimBrent

unkx80: This technique has existed for a really long time already, it is Hikaru no Go that has conveniently used it in its comic. There are variants in the order of moves, though.

[2] Dieter: That comment is somewhat outdated, because the superko strategy has been added.

blubb: How so? I don't see why trying to set up two kos means that there's no better response.

Furthermore,

  1. that's just one technique among several other suggested ones, and
  2. unlike in many games in practice, superko is presupposed.

5. Real life examples

  • Karami has a pro example. I don't know if it was mirror go, but when Black finally played on tengen, the position was symmetrical. And the move was decisive.
    • blubb: I have [ext] looked it up at GoBase. Upto that tengen play, the game indeed was some interesting kind of mirror Go, that is, not move wise, but joseki wise.
  • Bildstein/PositionsOfNote

6. Making sure that for the one who is mirroring, that his strategy is worth less than the komi.

(that s/he cannot win by more than the komi on the board)

If it is Black: E.g. if Black wins by 6 points on the board, than White had won by 0.5 point. tderz


This is a copy of the living page "Countering mirror go" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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