White should simply have extended with 24 as shown in Figure 7,
which makes the white stones stronger without helping the black
stones get stronger, too. This is another important Go
principle: often the best way to attack your opponent's stones
is to make your own stones stronger. Beginners like to say
"atari" and do it every chance they get. But it is often a bad
idea. In this game, it just made the black stone stronger
without helping the white stones at all, which is exactly the
opposite of what White needed. White 24 in Figure 7 strengthens
the white stones at the bottom and it attacks the lone black
stone, too. Now if White could play atari at 25, the Black stone
could not get away (try it and see), and so Black must defend it
by playing a move like 25 just the same as in the actual game.
But now White has only one side to worry about, and 26 is one
good move which will prevent Black from capturing the white
stones on that side. The marked black stones in the corner are
as good as dead. (More advanced r