: ( 454)
Black captures White's single stone, and simultaneously pre-empts a White move at this point.
: (99 458; 100 459)
White could also play at , instead.
White could also seek life for her group on the upper edge with a move at immediately, but must be on her guard thereafter.
:
Black cannot play at , instead, hoping to stop White from getting her second eye there. White will answer with the atari of , and - after Black's response with - capture Black's single stone with a move at .