Bent Four

    Keywords: Life & Death

Chinese: 曲四 (qǔ sė); 弯四 (wān sė)
Japanese: 曲がり四目 (magari yonmoku)
Korean: -

[Diagram]
Bent four  

The circled empty spots make the bent four shape.

Bent four is a live shape.

[Diagram]
Bent four  

A bent four is alive, because the points a and b are miai, so black can always form two eyes.

However, if a bent four appears in the corner, the status of the group may be different. See bent four in the corner.


[Diagram]
Bent four with cutting points  

When the bent four has cutting points such as that induced by the white+circle stones, it is not necessarily alive. This particular case is also known as 断头曲四 (literally, "decapitated bent four") in Chinese.

[Diagram]
Bent four with cutting points  

Due to shortage of liberties, W1 is an atari on two Black stones, forcing B2 to connect, allowing W3 to occupy the other vital point. Black is dead in a straight three dead shape.

[Diagram]
Bent four with cutting points  

Note however, not all configurations of cutting points cause the status to be unsettled. Also, one must take note the number of liberties on the individual chains. In the situation here, Black is unconditionally alive with four points of territory.


See also:


Bent Four last edited by MrTenuki on March 13, 2011 - 16:20
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