capturable-2

For a player's string, local-2 is local-1 and, recursively, any adjacent intersection without a stone of a string that is of the player and either uncapturable or capturable-1.

A player's string is capturable-2 if

it is neither uncapturable nor capturable-1 and
the opponent cannot force capture of the string's stones and prevent a local-2 permanent-stone of the player.

More formal versions of the definitions are in the Japanese 2003 Rules. The concepts local-2 and capturable-2, and the following example, have been discovered by Robert Jasiek.

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Example

Examples are rare but here is an example:

The marked stone is capturable-2.

Note that it is not capturable-1: if White captures it, Black can try to play a local-1 stone. However, White prevents this by playing on the intersection of the marked stone. Afterwards, Black playing there fills one of his own eyes so White captures the whole black group and then Black cannot establish a permanent-stone on the intersection of the marked stone.

This is the local-2 environment of the marked black stone.

The stone 2 is a local-2 permanent-stone. This proves that the original marked black stone is capturable-2 so alive.

capturable-2 last edited by RobertJasiek on December 16, 2019 - 09:36

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