Opponent mirrors your moves

xed_over · Post by **xed_over** » Thu Mar 21, 2013 9:28 am

hyperpape wrote:Here you go, xed: http://rongen17.home.xs4all.nl/Hikaru/index.html. The mirror go game was very short, and obviously not a professional game.

I looked there before I posted, but couldn't find the game. I still don't see it. Maybe I don't know where to look.

shapenaji · Post by **shapenaji** » Thu Mar 21, 2013 2:18 pm

Mirror go becomes fun once you know that you can always break the mirror if you want to. At that point it stops being a gimmick and is a real test of skill. I dunno, I guess the frustration with mirror go seems to be the same frustration that players have when they learn shiny new joseki and then their opponent plays a strange center oriented strategy, it's not cheap, it just bypasses their study.

Amelia · Post by **Amelia** » Thu Mar 21, 2013 3:13 pm

xed_over wrote:
hyperpape wrote:Here you go, xed: http://rongen17.home.xs4all.nl/Hikaru/index.html. The mirror go game was very short, and obviously not a professional game.
I looked there before I posted, but couldn't find the game. I still don't see it. Maybe I don't know where to look.

I didn't see it there either. As I'm watching Hikaru no Go right now and the game is very short, I put it together if anyone's curious.

Uberdude · Post by **Uberdude** » Fri Mar 22, 2013 6:01 am

Fooling around last night on KGS, someone played mirror Go against me as black with the tengen then mirror strategy. You can see how I just played normally (actually some of my moves were probably a little slack but I was confident he would not break the mirror as this was a rematch after I beat him and he was answering quickly, presumably thinking mirror Go was a good strategy to beat a stronger opponent) so split the board into 2 equal big and fairly solid territories and then started shenanigans around tengen with L11 that meant mirroring would obviously lead to me winning with komi so the fighting started and by move 58 at k8 the game is very favourable for white IMO as I have made the lower middle my territory, but black's upper middle is not his territory. In exchange he captured p10 but that's not so big.

SmoothOper · Post by **SmoothOper** » Fri Mar 22, 2013 10:03 am

Uberdude wrote:Fooling around last night on KGS, someone played mirror Go against me as black with the tengen then mirror strategy.

Last night I had someone play tengen for move one. I didn't mess around and played a contact move immediately. I don't know if it was a mirror go strategy or not, but that pretty much stops it. I guess if you are black and white mirrors, you can just play on tengen, but that might be slack. It doesn't seem to disrupt my low territory strategy much, to have a few moves in the center.

hyperpape · Post by **hyperpape** » Fri Mar 22, 2013 8:09 pm

xed_over wrote:
hyperpape wrote:Here you go, xed: http://rongen17.home.xs4all.nl/Hikaru/index.html. The mirror go game was very short, and obviously not a professional game.
I looked there before I posted, but couldn't find the game. I still don't see it. Maybe I don't know where to look.

My thought was that because it's not there, it's just made up. Maybe that doesn't add anything.

hyperpape · Post by **hyperpape** » Fri Mar 22, 2013 8:20 pm

I think part of what's scary about mirror go to certain mindsets is that the recommendations about how to counter it are involve

1) taking a local loss, as in the case where you contact tengen, or
2) very abstract.

I'm not scared of mirror go (I can't remember whether I've ever played against it), but I know that when I think about handling it calmly, I come up with nothing--I just don't know how to play so that mirroring becomes strategically bad. In that regard, the Kim Jiseok/Kang Dongyun game is very instructive, as is your game, Uberdude.

One question for Uberdude: can you elaborate on how you chose L11, and how it changes the game? Is the point just that L11 does much more work than J9 would, and did you base that move on a careful count?

Uberdude · Post by **Uberdude** » Fri Mar 22, 2013 9:42 pm

hyperpape wrote:One question for Uberdude: can you elaborate on how you chose L11, and how it changes the game? Is the point just that L11 does much more work than J9 would, and did you base that move on a careful count?

The idea of L11 is if he gets all the points in the middle above tengen, and me below, then tengen is certainly worth more than komi, no need to count really. But I can't play it on move 32 or it's too lonely and will probably die. So n8 onwards are preparatory moves to create a bridgehead into the middle area whilst playing vaguely sensible reduction type moves. Of course it might be better for him to not mirror n8 but answer at n10, split at o7 or something. Once I've got n10 I chose L11 as it's a shoulder hit to tengen so mirroring will be stupid (yes J9 does little work) but I didn't count anything (it was blitz after all). The idea is to turn most of that middle area into dame and then with our equal territories elsewhere white wins with komi. In fact if he blocks at k11 rather than o9 maybe he can make more points that komi in the h11 area but at least that is a small area, and I would still have the chance to fall back and try to make some points in the lower middle area having already turned black's potential points in the upper middle to dame.

gogameguru · Post by **gogameguru** » Sat Mar 23, 2013 1:56 am

hyperpape wrote:I think part of what's scary about mirror go to certain mindsets is that the recommendations about how to counter it are involve

1) taking a local loss, as in the case where you contact tengen, or
2) very abstract.

Maybe you're over thinking things a bit? It can be a little abstract, but nothing that's really any harder than many other aspects of go. When black mirrors, in particular, it's not that hard, because white probably has komi.

Go is all about trying to make your own stones work together efficiently and, conversely, trying to make your partner's moves become inefficient. Uberdude's game is an interesting example from that perspective. (Uberdude, I hope you don't mind some comments, I can see that you weren't taking the game particularly seriously)

The value of the tengen stone is important, so think about some ways that it can be used efficiently:

1. To attack. For example, to chase a group into the center and use it to block off the escape, or make things uncomfortable. In this way tengen can become a very effective move. This is often a good way to turn tengen into a good move in, say, a five stone handicap game too.

2. As a key stone in a large framework. This is harder to do well, but it also relates to the point above, because you never create a large framework expecting to keep all of it, but rather to pressure the other player into invading, so that you can attack and play actively while they have to defend passively.

3. As a 'universal' ladder breaker for all four corners. If you can play more severely in two or more corners, because of the latent possibility of a favorable ladder, you might be able to gain back more than the value of a move in those negotiations. Your stones should be working somewhat harder than your partner's in that case. Plus, tengen is still on the board

So, keeping those things in mind, have a look at Uberdude's game.

I don't know how to absolutely prove some of these things, but my feeling is that K3 is slightly bigger than K17, because black had more potential (with tengen) at the bottom than white had at the top.

Also, remember that black wants to use tengen primarily to gain an advantage through attacking, so allowing white O3 was questionable. I wouldn't have continued with the plan to mirror at all in this opening. I think black should play K17 at M3 instead.

O3 feels a bit bigger than F17 for the reasons already mentioned. White should be happy so far. I'd go so far as to say that white has a small advantage.

I felt that white R6 was questionable though, and P5 even more so. Remember that black wants to make sure that tengen remains an efficient move (as he does with all his stones) and make white's stones become inefficient. White wants to do the opposite.

A fighting game with running battles, or a center/moyo oriented game should be what black's looking for. A game with lots of small, settled territories - where the board is divided into small, localized struggles - should favor white. In an extreme case (hypothetical) where there were small territories all over the board and tengen became basically dame, white would win by komi.

Maybe this sounds too abstract? It's probably a bit unfamiliar because we're not used to dealing with tengen or mirror go, but it's something you can assess visually.

Look at the board after the exchange of R6 for C14. Two things have happened:

1. Black's gained potential on the left side which is enhanced by the tengen stone, while white's gained potential on the right which is reduced by the tengen stone.
2. The star point stones at Q4 and D16 have both lost their bases and are floating. A running battle in the center will be more favorable to black than white.

Continuing with the exchange of P5 and E15 compounded the problem. I think black was better at this stage. K3 has become a strange looking move, whereas K17 (while still strange) at least works with tengen to map out a large framework.

I can understand that these moves were motivated by fighting spirit, but the kosumi in the top left was a very big point. It would have been better if white had a stone at 6, but how about lightly erasing like this instead now?

In the diagram above (hidden to save space), if black pushes and cuts with a-c, white can play d to manage the situation. After d, x and y are miai. After black y, white x, the cutting stone at c can't be laddered (thanks tengen!) but if black tries to save the two stones at 6 and a, several moves like z will soon become double threats, because z (for example) also threatens to capture c in a net, starting with q. So black might play y at x instead, but then white will force with q and play y. The aji at B18 isn't an urgent problem for white and white can fix it with E18 later.

If white mirrors 7, there are a few possible moves, but settling in the top left with 8 seems good enough and better for white.

For similar reasons to those already mentioned, I think black should have stopped mirroring after white 14 (C6) and played the one space pincer at C8. O17 was alright for white, black F3 should still be the pincer (the bottom is small) and C3 seems better at R17. I won't do more diagrams because this is already a long post, but I hope you can grasp the feeling that the analysis doesn't have to be deep and complicated.

Uberdude · Post by **Uberdude** » Mon Mar 25, 2013 4:13 am

gogameguru wrote:(Uberdude, I hope you don't mind some comments, I can see that you weren't taking the game particularly seriously)

Sure. In fact I didn't realize he was mirroring for a few moves after he started and was just in the bloody-minded fighting spirit mode of "Oh well, you tenukid me so I'm not going to look at what you did and just follow up on my move you tenukid!"

. I agree with what you said of going for the p5 e15 trade being good for black as not only do those moves create territory (well not quite as 3-3 still lives...) on the inside, but influence on the outside and suddenly that means that black's tengen stone can work towards centre points which I then needed to do something about with the L11 tactic.

jts · Post by **jts** » Mon Mar 25, 2013 2:30 pm

There was a game on KGS - perhaps in January? - in which Black has a four-stone handicap, and they played mirror go nearly to the bitter end... but after Black broke the mirror, he ended up losing a huge group by one liberty. Did anyone else see that game, and remember who the players were?

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