Puzzle Confusion

I’m looking for some explanation for why this is the ‘solution’ to a puzzle…
Today’s daily Tsumego Pro basic puzzle is as follows…

The ‘solution’ is this…

Since A9 is Ko, Black’s next move has to be elsewhere, but I can’t find any other move that doesn’t lose them the three B3, B4, B5 stones. Since they’re lost anyway, aren’t there other variations that would also work? Or, I’m just missing something obvious. Thanks,

Puzzle

I’m no expert but s couple of thoughts.
Firstly, sometimes the answer to a puzzle is that you achieve a ko. If you cannot live outright then maybe seki or ko are the best outcomes you can achieve. A ko is better than dying completely.

Secondly, white can’t fill the ko here for to self Atari. So white needs to take the B8 stone. But this gives black another ko to return to this position but now white can neither fill at A9 or take B8 so unless white has a good (i.e. big enough) ko thread black will then take at A9 again and the four stones are in troubled and the three black stones nearly saved.

As you said you can’t find any other way to save the three stones. So a ko fight is worth a try!

4 Likes

According to Sensei’s Library (Tsumego Conventions at Sensei's Library), this is the order of most to least desirable outcomes in a defensive tsumego:

1. local life (including by double ko) or escape from the play area

2. seki (I’d also distinguish sente seki as preferable to gote seki)

3. approach ko in defender’s favour

4. direct ko, defender takes first

5. direct ko, attacker takes first

6. approach ko in attacker’s favour

7. death (obviously)

Within these seven or eight bands, distinction can also be made by pointage and the amount of ko threats left in the position.

The key thing to understand is that tsumego are isolated from the rest of the board. A classic example is the conventional preference for seki rather than ko: this assumes that the attacker has more threats than the defender, but this information is obviously not available as the rest of the board isn’t visible.

Tsumego conventions can be considered a “simple model of a realistic whole-board environment” which allows the tsumego creators to avoid having to actually include a whole-board position.

4 Likes

I agree with @teapoweredrobot - the three black stones are in serious trouble. The only chance to save them is ko. That alone is enough for it to be the correct answer. Plus there’s the fact that white has to win the ko three times to live locally, which is a tall order in most games; so either black profits locally, or black profits elsewhere when white ignores Black’s ko threat. Either way, good for black.

2 Likes

I’m still having trouble seeing how black doesn’t automatically lose the three stones at the bottom no matter what they do. After wB9, doesn’t black have to go C8?
There’s nothing Black can do at A3 or A2 that doesn’t put them in atai and loose those three stones instantly. So after C8, can’t white just go A4, or A3.
Black can try to take back at A9 but then the threat to white’s stones at the top is removed as soon as white captures the three black stones below…? I def feel like I’m missing something.

Black makes a ko threat which white must answer (J9 and J8 in the below but you have to image the actual situation!) and then black takes at A1

Now white needs a ko threat big enough to keep the fight going. If not then black will save the three stones

1 Like

As a rule of thumb you should consider only the local moves. Here Black has no ko threat so will have to connect (and then lose 1 point.). Then white will have to hurry up to go back take the 3 black stones.

If w don’t play for a ko then black will do and same no local ko threat. Then if you didn’t anticipate, which meaning is you start to take a liberty of the 3 black stones at A3, it’s going to turn into a drama for white as the 4 stones will be in Atari.

Note: from your opening post, I assumed the problem is “white to play”

Thank you, teapoweredrobot!

I think your first explanation had all the information I needed but I couldn’t connect the dots until your second reply. I understand now. I was ‘stuck’ thinking they were lost stones, which they are unless, to your point, there is a larger ko threat somewhere else to which white needs to respond allowing black to recapture at A9. I still mainly only play 9x9 so it didn’t make sense to me until considering stone that I couldn’t see.

Thank you again.

2 Likes

Have you any offhand examples of a defensive sente seki, that is where you save your own group by making a seki in sente? I can imagine a lot of sente sekis while attacking when you threaten to kill but the best resistance leads to a seki.

1 Like

I imagine that you could have a sente seki if you are surrounded by some diagonal moves and you push in it forcing black to connect and creating a big L shape with 3 stones inside (from memory)

This: Go
If I don’t misunderstand your question.

It’s a sente seki for White but they’re the attacker, which I’m suggesting is the usual case.

Whereas in Bugcat’s post they said

If I’m the defender in the tsumego, i.e. I need to make two eyes or a seki etc to live, then any example where I do so in sente?

I guess the main issue is that once a group is alive whether the living move is gote probably depends on how big a threat it is.

I guess something like this position white can choose to live with two points or get a sente seki, sente assuming there isn’t a bigger move worth ~20 points gote.

White needs to play the last move at J1, so it’s certainly not sente for white?

If it’s worth giving up sente is a different question of course and depends on the whole board situation. But in a way, that’s true for any tsumego, isn’t it? (Even a 30 points kill can be a bad move.)

I forgot about that woops. But it’s not a “sente seki” for Black either because they don’t initiate it. So gote seki for white would be a better classification I’d say. Compare to the example I gave instead, where White can choose to initiate the seki, but it’d be very silly for a tsumego though (there’s not really an attacker or defender in that situation either).

Well maybe. Sure sente depends on the whole board position and tsumego sente is more like local sente, as in if it would cause you to fail your objective then it’s sente.

Hmmm, black plays the first move after the initial position. So what do you mean by ‘initiate’?

I think we’re getting into “what is a/the puzzle” territory. In that position I would imagine one way it could be phrase is “Black to live”, and after the first correct move black is alive, either with points if Black moves again or in seki if White chooses to make it.

But there’s no forced continuation of the puzzle for White, White can tenuki since Black achieved their goal, so really it’s life in gote.

If the Black move is already played, maybe the puzzle would read be “White to make a seki” which as you mentioned would be a gote seki for White.

I just think the idea of a sente seki for the ‘Defending player’ seems a bit odd, without examples . On the one hand if it’s a seki either there’s already two groups which could both be captured that end up a seki (in which case who’s the defender? the person who plays second? ), or like in your example instead it could be a new group created inside that lives in seki, and it seems like the person creating the group inside is probably the attacker.

1 Like

I’m probably missing something, but form my simplistic perspective it’s just this: There is a starting position and the question: ‘What’s the best can black get here locally?’ Answer: ‘Seki.’ Bonus question: ‘After reaching the seki, will black have sente or gote?’ Answer: ‘Sente.’ So I’d say ‘black gets seki in sente’ is a very fitting description for the situation. Remove the stone on L3 and you get a ‘black gets seki in gote’ situation, so it’s actually useful for distinguishing between 2 different cases.