This is today's game in Korean Kuksu tournament: http://www.go4go.net/go/games/sgfview/43596

Lee Sedol 9p (Black) vs. Park Yeonghun 9p (White)

While fighting the ko at 'a', black appears to be a loss-making threat. But I did not realise at the time that black can not only create many ko threats but also form an 'under the stones' later. Can you see it?

Click Here To Show Diagram Code

[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . X O a O . . . |
$$ | . . . X O . . . . . . . . X O . . . . |
$$ | . . . X X O . . . . . X X O O . O O . |
$$ | . . X X O . O . O X . X . X O O X O . |
$$ | . X . X O O . . O . . X X . X . X X . |
$$ | X . X O . . . . . O O . O X X . X . . |
$$ | . X O O O . . . . X O O O X . O . . . |
$$ | . . X X . . X . X X X O . O . . . . . |
$$ | . . . . . X . X O O O . . O . O . X . |
$$ | . . . , X X X O . , . O O X . , O X . |
$$ | . X X O X O X O . . . . . O O O X X . |
$$ | . . O X O O O O . . . O . X X X O X . |
$$ | . X O X . O . . O . . O X . . O O O X |
$$ | . O X . X X O O . . . . O . O O X X . |
$$ | . O X . X . X X X . X . O X . . O X X |
$$ | . O O X X X O O O O . . X O O O . X . |
$$ | . O X O O O X O X X X . X X O . O X . |
$$ | X X X O O O X X . . . . . . 2 1 . O O |
$$ | . O O O . X O . X . . . . . . . . . . |
$$ +---------------------------------------+[/go]