Tsumego From Games 17 / Solution

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Cut: seki  

If Black simply cuts at B1, he has an eye. I see no way to avoid seki.

1. Main line

Spoiling the shape  

Black has to spoil White's shape.

Main line: a ko  

White cuts at W2, producing a ko.

Main line: a ko  

Black winning the ko. Playing B3 is better than playing at a.

Main line: a ko  

White winning the ko.

2. Variations

Var 1  

If White protects at W2, Black throws in at B3. If White blocks at W4 ...

Var 1: continuation  

Black has an eye in the corner accounting for three liberties. The inside liberty at a and the false eye are two more liberties. White has one outside liberty and an approach move liberty at b. Black is far ahead in the fight: I believe he can omit B3.

Var 2  

If White cuts, Black captures. W3 prevents the connection underneath at a. B4 at B2. W5 again prevents the connection underneath at a. B6 wins the fight.

3. Failures

If Black attempts to do better than the ko in the main line, he will end up worse.

The (forced) game sequence  

If Black wants to do better, B1 looks like the only possibility. White makes an eye with W2 and threatens to capture the black group in a snapback. B3 thus is forced. White's placement at W4 is tesuji.

3.1. Counterplacement

Counterplacement: main line  

If Black makes a counterplacement, W2 must connect on the inside (see further comments). B3 is a first possibility. W4 and B5 both make an eye. W6 and B7 prevent the second eye.

Counterplacement (ctd)  

After Black throws in at B1, White has one eye liberty and three outside liberties (a, the marked stone and b). Black has two eye liberties (see big eyes can be small in the corner) and one outside liberty. In this eye versus eye capturing race with two small eyes, White is alive. Black counts the inside liberty to defend but the number of liberties is then the same and White has sente. White kills.

Variation at 4  

Another way for White to win the capturing race is W1 here. For one thing, Black must be very careful not to make an eye at a: see eyes that lose liberties example 1. But even if Black cunningly starts taking away outside liberties with B2, White has three outside liberties left, the approach move at b included. She will eventually play a to atari Black.

Variation at 3  

If Black cuts off the placement with B1, White still makes her eye at W2. If Black a, White b reverts to the counterplacement main line.

The game sequence: variation at 1  

In the game, B1 was a big mistake but so was W4. The next diagram explains how White should have won the capturing race after B3.

Connecting from this side  

After connecting here, White has four liberties (including an approach move) against Black's three.

Variation at 3 in the game sequence diagram  

This way it is two against three again.

3.2. Cut

If Black simply cuts at B1, he has an eye. I see no way to avoid seki.

Cut: seki  


When fighting a semeai, mutual liberties should be taken last. Black had to cut off W4, get one eye, and then attack from the outside only. Then he gets an easy seki. Of course, it the game Black got more, but that was only because White could not count liberties.

These are the capturing race principles:

1. Eyes win semeais

2. If you are behind, make a ko

3. Make a double ko if possible

4. Takeback wins a tempo.

5. Attack from the outside; mutual liberties have to be filled last.

6. Ugly forms win.


In order of appearance

Tsumego From Games 17 / Solution last edited by on June 24, 2006 - 07:54
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