Mirror Go is not seen too often - especially in pro games - so it was surprising to see it played by Lee Sedol in a recent Chinese city league game. Lee Sedol, playing white, was mirroring black for a while, but black played tengen at move 23 and shook him loose.

So I am wondering if a typical pro would find white's behavior to be rude? If not, how much longer could they have kept this up with it still being proper?

Go seigen played mirror go to move 64
Would it be considered rude? Wouldn't it just be a matter of whether or not it works?

If you're white and black mirrors to the end, you will win by komi, so why should you think it rude?

I have written about this extensively elsewhere, but the short answer is that many pros have found it rude. It led to the famous Tokatei stand-off where a player refused to play Fujisawa Kuranosuke, Kitani objected to Go doing it, there were calls to ban it, and it is speculated that the old Chinese starting stones were introduced to combat it. In Korea Seo Pong-su famously not only mimicked Cho Hun-hyeon repeatedly but even repeated the same mimicry patterns over and again.

Two things changed opinions. One was the introduction of komi. But probably more important was Yamabe Toshio finding a definitive counter-strategy. It was so effective that even Fujisawa, trounced twice in a row by him, finally gave up playing mimic go.

NB 'mirror go' is inaccurate. 'Mimic go' is correct. And in Go's case it was mimicry only after tengen.

I don't know if this is a fair characterization of what happened. Already was not a mirror move, but the position then became symmetrical again after . And again at white does not mirror, but after a few moves the position turns symmetrical again. So actually both players are cooperating to create a mirrored position, (E.g at , black is working towards a mirrored position).

Mirror is not rude but as valid a strategic concept as any other. It is the opponent's task to devise a counter-strategy. Blaming the mirroring player is not a counter-strategy but can indicate the failure to find some. OC, there are counter-strategies also for no-komi go.

Actually, on the board, mirror go can never become rude because it cannot become worse than the opponent's play. Mirror go can only become strategically stupid if mirroring for too long and, under no-komi go, losing obviously by the too simple strategy.

Note that my question was whether professionals found this behavior to be rude, i.e., their own personal reaction. Not whether philosophically it ought to be considered rude. Nor was my question about whether it is mechanically possible. Robert seems to think anything within the rules cannot be considered rude, which seems to ignore the fact that the game is played by humans, with preconceived ideas about fairness, sportsmanship, etc.

A slight tangent: Many times in team sports, when the other team is getting blown out, the winning team will take out their starters so as not to excessively run up the score. Sure, there is nothing in the rules that keeps them from doing so, but there is this thing called etiquette that does. I do think mirror Go violates basic etiquette or sportsmanship for many, but I wasn't sure what the reaction would be in a pro game.

Really, why? And if so isn't this their problem?



I wonder if the answer Go got was - "yes - but it will really upset them." And that is why he played it.

Well I guess it would depend on the individual, but here's my view:

- As John said, there is an effective counter strategy.
- By mirroring your opponent's moves, you are not saying "I can win by outthinking you." Instead, you are saying "I can win by assuming you don't know the refutation."

For me, even playing hamete josekis is more proper than mirroring, because they are confined to one part of the board and one phase of the game. Trying to win by mirroring is trying to win with minimal thought throughout the game. That is why my original post asked the question at what point does it become rude to continue mirroring?

The thread title suggests the philosophical side.



If you want to discuss this and hear my statement about what I think about this, then I guess the go rules forum is the appropriate place.

Speaking as someone who plays mirror go with white occasionally, that's just not true at all. I can't even.

Tangentially, I think I heard playing mirror go in handicap games is rude, which I agree with (because you started with an asymmetric advantage).

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Could someone please elaborate more on the effective counter strategy?

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I suspect you’re a much stronger player than I am … but my spontaneous answer is: “The effective counter strategy would be just to play the best move, considering the whole board, not necessarily a direct reply to the opponent’s last move.”

And on second thought: “Tengen! Tengen!”

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JF/TMark wrote about Yamabe's counter-strategy in their New In Go column, which is unfortunately no longer online, but if you have the GoGoD CD it's on there.


If your opponent knows what they are doing, tengen to break the mirror is often a bad move (worth less than komi).

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