Capturing Race Exercise 13 / Solution

is the key move...  

threatens to make life in the corner, forcing . An extra approach move is necessary to capture giving black time to capture the white stones on the outside.

Filling inside first doesn't work for white either  

If white tries to fill inside first with , black captures leaving a 3-space big eye to fill. or at has the same result.

Failure

Failure  

here looks like it does the same thing, but actually invites ko. Black doesn't have time to play at to prevent the ko - that will lose the race outright.

Failure  

If simply reduces White's liberties, and can turn the corner into a ko.

Failure  

Although makes a squared four, it does not have five inside liberties, since big eyes can be small in the corner. Instead, it has only three inside liberties, so White wins the capturing race.