Two-space notchers not fully connected

    Keywords: Life & Death
[Diagram]
Black can live  

So long as a is not occupied by White, Black can live (provided Black plays first). The vital point is at b.



Black can live

[Diagram]
Black can live (correct play)  

The placement at W2 won't work. After B3, a and b are miai, so the black group has two eyes.

[Diagram]
Black can live (correct play)  

Black has to be careful in responding to the hane at W2. Only playing at B3 will live. Playing at a is wrong.

[Diagram]
Black can live (wrong play)  

Playing at B3 is wrong. White makes a placement tesuji at W4, causing an exchange at B5, followed by connecting at W6. Black faces a shortage of liberties - being unable to play at a - and dies because the eye on top cannot be formed.

[Diagram]
Black can live (wrong play)  

B1 is a very careless move. W2 is a tesuji, followed by the atari at W4 which destroys an eye in sente, and then W6 destroys another eye. Now Black is dead.

[Diagram]
Black can live (wrong play)  

B1 is also wrong. White plays a placement at W2, followed by cutting at W4 in sente (aiming to capture three black stones at a), before making the final killing move at W6.

[Diagram]
Black can live (wrong play)  

The descent at B1 is incorrect as well. White can kill the group with a hane at W2 (aiming to capture two black stones at a), followed by a placement at W4. B5 attempts to divide the space to make two eyes, but the connection at W6 leaves Black with a shortage of liberties, and Black cannot play at b to defend the second eye.



White can kill

[Diagram]
White can kill  

If White starts at b, Black's 222WN notcher dies (2 and 3 are miai). Either hane (5 or the other one) kills as well (White gets the second hane or nakade). White can also kill from outside by filling circle (222WW).

Starting with 2 would let Black live (with 1). Therefore W1 fails if white+circle is one to the right (222NN), but hane still kills. Actually hane kills any 222xy.

If the lower leg is longer (223WN), White can not kill (hane is met with 1, and 1 with 2). Neither if the upper leg is longer (223NW, similar).



Two wedges kill

[Diagram]
Black is dead  

The two white+square stones make it impossible for the black group to live, even though it has extra liberties outside. Try figuring it out yourself, using the last three diagrams in the "Black can live" section as reference.

The solution can be found at flying saucer shape (222WW).


Two-space notchers not fully connected last edited by RobertPauli on January 20, 2018 - 14:26
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