Lee Sedol - Gu Li, 4th encounter
Black treats the stones involved in the corner exchange as forcing moves and uses their influence to make the big extension at . The clamp at is a common technique to attack these stones so that they cannot be easily sacrificed. For example, if were at immediately, then Black would sacrifice and play at himself, which would be a smaller sacrifice than the game sequence.
Instead of firmly capturing the cutting stones in the lower left, splits the upper side. After a common exchange of pressure and escape, and take the last big points. defies the common knowledge to play at the centre of three stones (a) so there remains some aji in that shape.
exploits the aji immediately and forms an empty triangle. Eventually needs to return and capture the cutting stones, so that the solid connection at has made strong influence in sente. White's stones are facing less open area and the opening now seems favorable for Black.
splits the lower side and exploits the aji of the two stones once more. We can say they have done their job! On the other hand, White's left corner is very strong, so the job of splitting is more destructive of White's territory than it weakens White's groups.
The cap at tries to attack the black stones on a large scale.
peeps and provides some support for the stones at the right, so that can take the time and strengthen the central stones. After Black seems to be firmly in the lead and looks like an emergency measure.
While White links up his invasion stones to his lower left group, Black uses the obtained influence to attack the upper side with . The flow remains in Black's favor.