I'm going through the problems on GoChild, and it marks my answer as wrong but I can't see why. The problem is #98 of the Basic 900 Connect and Cut pack:

Click Here To Show Diagram Code

[go]$$c
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O . O X . . X O . . |
$$ | . . X . . . . . . X . . . |
$$ ---------------------------[/go]

My answer was at F1, and a response at E1 shows as wrong. But capturing with at E2 strikes me as a perfectly valid solution. What am I not seeing?

Click Here To Show Diagram Code

[go]$$c
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 3 O X . . X O . . |
$$ | . . X 4 1 2 . . . X . . . |
$$ ---------------------------[/go]

Click Here To Show Diagram Code

[go]$$c
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 5 O X . . X O . . |
$$ | . . X O 6 O 7 . . X . . . |
$$ ---------------------------[/go]

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

E2 makes a ko. This gives white a chance to keep you separated and kill at least one of your groups. There is a better answer.

Edit: which you can see above, if Magicwand doesn't hide it...

_________________
Patience, grasshopper.

Click Here To Show Diagram Code

[go]$$c
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 3 . X . . X O . . |
$$ | . . X . 2 1 . . . X . . . |
$$ ---------------------------[/go]

ko

I saw that it's ko. There are no threats for white so the only response is to connect at E4. Maybe I just have an aversion to calling the solution wrong just because it's not exactly what the author wanted. And capturing 5 stones is optimistic when white can connect after the peep (that's another solution GoChild accepts).

9stone:

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[go]$$c
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O 4 O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 2 O X . . X O . . |
$$ | . . X 5 1 3 . . . X . . . |
$$ ---------------------------[/go]

With ko in go problems, you have to assume that there MAY be threats elsewhere. For that reason, ko is worse than life. And for this connection problem, if you can connect without ko, it's superior to ko. So gochild is hoping for something like this, as 'ideal for both sides'. If W could separate black, W could kill at least one side by making it a dead shape. However, by connecting, black saves both. White can't play 4 @ 5 because then she would be in atari.

_________________
Someday I want to be strong enough to earn KGS[-].

Click Here To Show Diagram Code

[go]$$c white can't play a
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 2 O X . . X O . . |
$$ | . . X a 1 3 . . . X . . . |
$$ ---------------------------[/go]

It's not that black can necessarily capture stones, but if w connects after the peep. black connects and is unconditionally alive. Usually when doing this type of problem, we assume that there are ko threats elsewhere, even if they are not shown on the diagram, and if it's possible to survive without ko, then that's better.

_________________
Patience, grasshopper.

These connect and cut problems make me feel like I'm too stupid to play Go. I nailed everything up to them, and now I don't get any.

Oh, don't worry, they're really tough. If you have a bad time with them, you can always work on a different set and come back later. That set and some of the endgame sets are particularly merciless.

_________________
Someday I want to be strong enough to earn KGS[-].

That's good to know.

Starting out, I found "connect and capture" and shortage of liberties problems to be difficult to grasp at first--keep practicing and you'll get the hang of it.

I looked at the connect and cut series and got a few of them wrong on the first try, and then I　ｒｅｃｏｇｎｉｓｅｄ　a problem from what I　ｔｈｉｎｋ　ｗａｓ　ａ　ｄａｎ－ｌｅｖｅｌ　ｐｒｏｂｌｅｍ　ｂｏｏｋ．　Ｓｏ　ｄｏｎ＇ｔ　ｇｅｔ　ｄｉｓｃｏｕｒａｇｅｄ，　ｈｅｈ．．

Not so, as I shall show below.



Oh, go players are quite aware that a problem may have multiple solutions. That is not the case here. There is only one solution.



It's not another solution, it's another variation. For Black to have a solution, it has to work for every reply White could make. In fact, capturing the 5 stones is the key variation because Black has to see the tesuji combination of throwing away three stones to reduce White's liberties. GoChild should not really accept a solution that does not include that variation. (IMO, it should not accept a solution without both variations.) In real life, White should not choose that variation, but this is a problem for Black, not White.

WHy is ko not a solution? First, because it is unsure. If there is a sure way to kill or live or connect or cut, ko is not the solution. (Sometimes double ko is the solution, if it provides a sure way.) One reason for that is that you may lose the ko in real life. The problem does not show the whole board, so we do not know the ko threat situation. (Oh, looking at the diagram, perhaps GoChild shows the whole board. It should not. If this were the whole board, Black could resign. ) Let me illustrate the other reason below.

Click Here To Show Diagram Code

[go]$$Bc Real life variation
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O 4 O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 2 O X . . X O . . |
$$ | . . X 5 1 3 . . . X . . . |
$$ ---------------------------[/go]

connects. White can save and as ko threats.

Click Here To Show Diagram Code

[go]$$Bc Ko
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . O O . . . . . . . . . |
$$ | . O . . O . . . . . . . . |
$$ | . . O O . O O O O O O . . |
$$ | X X X X O X X X X X O . . |
$$ | . . X O 3 O X . . X O . . |
$$ | . . X 5 2 1 . . . X . . . |
$$ ---------------------------[/go]

elsewhere

is the correct response (almost regardless of the rest of the board) to . The ko is humungous, and in real life White will not have a ko threat that Black should answer. But White should make the ko, anyway. Making the ko forces Black to make two net plays to connect instead of one. White sacrifices a few stones for an extra play somewhere else. (It is conceivable that there will be no play big enough elsewhere for White to make that sacrifice. However, the possibility that there is is enough for not to be part of the solution when Black has a sure connection in one net play.)

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

beginner - ko - problem 140

i think there is no need for ko to live or am I missing smth?

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[go]$$
$$ -----------------
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . X . . . . . |
$$ | . . X X X X . |
$$ | X X O O O O X |
$$ | X O . . . O X |
$$ | . . . . . O . |
$$ ----------------[/go]

i dont see any way to kill this group

Click Here To Show Diagram Code

[go]$$W
$$ -----------------
$$ | . . . . . . . |
$$ | . . . . . . . |
$$ | . X . . . . . |
$$ | . . X X X X . |
$$ | X X O O O O X |
$$ | X O . . . O X |
$$ | . 1 . . . O . |
$$ ----------------[/go]

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

thanks, that's what I thought.

but since I have a blind spot with some techniques and a few beginner problems seemed impossible at first glance I wanted to check

I can second that. It seems that correct answers that are just a little bit inferior to the chosen solution are also marked wrong. The connecting and cutting set on gochild is indeed quite unforgiving.

I still have problems with the connect and cut problems. Heck, I can't even get past the Entrance level problems.

Its trying to teach me what should be fundamental shapes that I just never learned as a beginner. I'm slowly starting to see and play these shapes in my games.

My favorite cut and connect shape is:

Click Here To Show Diagram Code

[go]$$B cut and connect 31 (black to play)
$$ ----------------------------
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . X , . . , . . , . . . |
$$ | . X . . . . . . . . . . . |
$$ | X O X . O . . . . . . . . |
$$ | . O X . . O O . . , . . . |
$$ | O O X . . . . O . . . . . |
$$ | . O X . X . . O . . . . . |
$$ | . O O O . . . O . . . . . |
$$ ---------------------------[/go]

_________________
My "guide" to become stronger in Go