Hi, before white played his last move (A3), the evaluation was +22 for white, after he played it, the evaluation changed to +6 for black. What is going on? Do you have to be the all-seeing engine to understand this sudden evaluation shift or is it understandable by a total newbee like me?
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A3 allows Black to capture the 2 White stones with D2, and it should be at somewhere like D2, E2 or E1 instead to protect those two stones.
After that, the White group at the bottom has only 1 eye, and White must play A2 to remove the second eye for the Black group.
It will turn into a seki on the bottom, with both groups with one eye unable to capture the other. In total, White loses around 17 points of territory (the points along the bottom as well as the 8 points for capturing the 4-stone Black group at B2), whilst Black gains 2 prisonners by capturing.
Edit :
An example seki sequence is D2 A2 D1 F1, after which if one side fills the inside, shared liberties at E1 and E2 they will never be able to capture the other group without putting their own group in danger of capture.
(For example, if Black E1 and White C2, Black C1, White A4, after that example seki sequence, then Black E2 would allow White to atari at A1.
If Black plays the same sequence at E1 C2, C1, A4, then G2 instead, now if White G1, neither White nor Black can ever fill the remaining last liberty at E2 without putting their group into atari.)
(atari at 8 if Black tries to fill the remaining inside liberty)
(same for White, if Black passes or played elsewhere (nowhere to play on this board, but on another board position which isn’t finished, Black would play away), Black can atari if White fills E2)
(So it’s impossible to capture for either side, and both players can play elsewhere.
Also, if either side fills one of the outside liberties, the other side can simply fill the other and maintain the seki)
In this type of situation, by the way, the throw-in moves at G2 or C2 are often important to play to make seki (to tie up liberties), and can be useful to know
Edit edit : Added images
Edit edit edit : Updated/added clarifications to the images and sequences ^^
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Thank you for your thorough response with images!
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My pleasure ^^
fuseki3: Just out of curiosity, at what rating is a player expected to being able to spot the tactics you described?
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The general principle here which you failed to follow (which is a very common beginner mistake) is: when your opponent has some stones thrashing about inside your territory which you think should be dead, don’t fill in their liberties to try to capture them, instead defend your weaknesses and if they don’t have space to make 2 eyes they are just dead already.
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Hmm, I think that that depends on the player. Everyone has a different style, and different strengths and weaknesses (for example in deep reading, or noticing relative strengths/weaknesses of groups, potential to reduce their eyes, etc)
I think most players around 15k+ would definitely notice that the 2 stones are capturable. Possibly even as low as 20-30k depending on the player.
In terms of noticing that the White group has only 1 eye if Black captures, probably most players 6k+ would notice that, and also some DDKs (double digit kyus) could spot it too.
Seeing the potential for seki varies, maybe also at around 3k-8k+, a lot more players in general would notice that potential ? I think some DDK would notice and try for it, too.
As for reading the entire sequences (and all of the counter-refutations to branches I laid out) from the outset, I think that it really varies based on the player and time-settings.
Most low-to-mid-dans I think can read that if they decide to, and probably some percentage of higher SDKs (around 1k-4k) ?
But there are always outliers, for example I have a very local/fighting and technical/reading-oriented style, so this sort of tactic & reading all possible sequences was clear to me I think around 6-9k, but some other aspects of my game like global tactics or direction of play were often weaker than average, so I’m possibly an outlier)
(or even making good shapes – sometimes fighting players manage fighting with shapes which are supposedly “bad shapes” yet managing to make it work somehow)
And especially in relatively one-way possibility sequences, I think one doesn’t always need to be able to read it fully to play the best-looking possibilities, and to try to capture something like the 2 stones at D2, and play it out + see the best moves as one plays through it.
I think some players might choose not to read it in this type of situation, even if they can if using relatively short time settings, or some might not put the effort in especially if it’s not needed because the best thing to do on the board is to just try it.
And many players even at 10-20k+ might simply wander into that sequence or something similar, just by seeing there is something there, and looking for each of the best moves at every point rather than reading it out.
On a related note, there are actually a few good basic concepts and shape tesuji to know from this set of sequences, too.
One of the other issues in this position is a tesuji Black can play at F1 to remove the White group’s eye, if White doesn’t respond to A2 at F1.
(It makes the G2 area eye false due to E1 and H3, which is a very good diagonal shape to know makes an eye false, and ties up the White group’s liberties.)
When we have a capturing race with 1 eye vs. no eyes, the group with no eyes has significantly less liberties and the one-eyed group often wins.
(due to filling the internal liberties potentially putting the no-eyed group into self-atari, whereas that doesn’t happen to the one-eyed group unless all outside liberties are filled)
It’s also impossible to make life in seki when it’s one eye vs. no eye.
So keeping one eye in capturing races, and avoiding being reduced to 0 eyes, tends to be important.
The other issues would be making sure not to fill one’s own liberties, for example by playing move 4 at E1 instead of F1.
That would shorten W’s liberties and allow B to capture the W group.
(Usually in capturing races, making shapes which can be ataried or forced in sente to fill up one’s liberties whilst connecting, loses liberties, and making solid extension shapes like playing White’s move 4 at F1 where one can’t be forced to connect/fill anything, is much better for extending liberties.)
That can be easier to see with some experience or knowledge.
If you’re interested in some of the capturing race concepts, false eyes and sekis, there are some interesting Sensei’s Library pages on some basics here :
Edit : It’s good to know that seki is a possibility in this type of situation with one eye vs. one eye (or groups with no eyes vs no eyes and shared liberties, at any level, I think.
It can be a very useful way to live with potentially dead stones inside opponent territory or reduce the opponent’s points when you can build a group + gain an eye like that. ^^
Also good to know that reducing opponent groups to no eyes, preventing them from making an eye, tends to be important, and tends to help win potential capturing races.
(Groups with no eyes tend to be much weaker than groups which have one, and often not able to run anywhere in solid opponent territory or counterattack effectively.
So best to defend cutting points/weaknesses and keep them eyeless/weak first if they are already surrounded inside your territory, rather than remove liberties from them, as Uberdude said – once a group gains 1 eye, there are many more potential options. ^^)
(Edit edit: Edited a few sentences a bit for clarity ^^)
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Thanks, i have a lot to dig in to!
So far i have only watched a few of Michael Redmond’s go beginner videos on youtube to learn the basics of the basics 
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Ooh, so very new, then, that brings back nice memories of learning the basics of eyes, capturing races, etc. when I was new to Go
I’ve seen some of Michael Redmond’s beginner material recently out of curiosity and enjoyed how it was put together. (I think a video about playing Go on the 13x13 board – I found it very clear. ^^)
Hope you enjoy and good luck with it ! ^^
It’d full normal that all these explainations will be over the head. Happy gaming!
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Haha, yes, very ^^
I didn’t realise how new you were, especially as your shapes in that board position looked really rather natural and good.
It has a nice flow to the game/stones, and an overall coherence in them, which I can see (some of how the stones developed) from the board position you posted, and is rare after total beginner games.
(and no noticeably bad or “torn”-looking shapes where one player let the other cut through a big gap in a key area (common mistake to see these torn shapes post-game for beginners, and even above 10k), which is also rare )
(only c7 is maybe inefficient and makes a double empty triangle, which is often an inefficient or bad shape if there is a better move available – for example a jump at b7 to defend more efficiently if you think the upper left corner needs defending)
(If you were White, F2 is a pretty way to have defended the g2 cut and makes nice eyeshape for your group, for example, and you and your opponent both played the E9 and D9 connection/forcing moves and response well at the top where Black could have done that in return in sente if you hadn’t, which is a good endgame shape/tactic).
(Black made the correct local choice to make a first-line cut protection, defending at F8 after D9 too, which beginners often don’t notice needs defending, or conversely see that E9+D9 is a good endgame for White.)
(If you were Black, then Black also has a lot of nice shapes on the right side which are very natural, like the H5 G4 G3 F5 double tiger’s mouth ^^)
So I thought you might already even be 17-22k or better, with a good basic understanding of various stuff, or knowing of eyes/seki/capturing race existing, and some shapes. ^^
Apologies if I made it too complex, hopefully if it goes over your head it’ll be something interesting to dig into for the future. ^^
(And either way, a lot of the shapes/flow of stones in your game I can see are very natural and nice, especially for a very new beginner, so very nice start ! )
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Thanks! I was black in this game. I will definitely go back to this thread when i have levelled up a bit
Even if some explanations were above my level, it was still interesting to get a glimpse into the vastness of this game. Learning efficient shapes, general principles and spotting threats is my focus right now (and maybe actually win a game during the process, haha)
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