Introduction
The lesson video is the following
Main position
In this lesson we have seen common move that follows the classic joseki shown below.
Getting influence
If black wants influence, then the shoulder hit at 1 followed by 3 are the key move. The response at 4 from white is important, as a black move at 4 would be quite painful.
At that point, black can choose to either connect at A, the most common choice to make influence, or connect at B to enfasis more on the center. Finally black can also choose to tenuki (C) as shown below.
In this case, black must endure and give up the corner, but he can manage to strengthen his wall.
Invasion
If black has a stones on the marked stone in the next diagram, then white position is open to be invaded. Black can choose between A and B.
Invasion at A
When black invades at A, white has two choices. Blocking at A or cutting at B, in both case with the aim to escaping to the center.
Blocking on the top
If white choose to block at A, the following continuation should be played.
At that point, white can choose to tenuki, but he must be careful as the next sequence could follow.
White is now a floating group and it is not possible for white to live locally. So to be able to play tenuki, white must be sure he can escape.
Cutting black
White can choose to cut black with 7 in the next diagram. The moves to 9 are played and black can chose to take a big corner with A or continue to harass white with B. Note that if black tries to save his stone by playing 9 at A, then white clamping would lead black to a disaster.
If black chooses to continue to harass white with 9 in the next diagram.
Then black will sacrifice his two stones (9, 6) to give white bad shape before he takes the corner with 19. White ends up with a bad shape and is not locally alive.
Invasion at B
If black choose to play at 6, then white can think of three answers. Hane on top, hane on bottom and clamping.
If white choose to hane under then black can cross-cut. What ever white choose to do, black will be able to isolate one of the white stone. For instance if white atari at A then black can play B to force the capture and isolate 5. On the other hand, if white atari the other side, then black can atari at A and start to cut 3.
If white choose to hane on the top, then black simply connect with 8 and 10. White cannot cut with the sequence A-B-C because black can live locally. In this configuration, the hane on top doesn’t look very good.
Finally, if white clamp, black calmly plays up to 13, taking sente and influence on the top. Later on, the black move A in exchange for white B is sente.
White continuation
If white has a stone at A, then white as a strong continuation against the corner.
After white block on the top, black can try to keep the corner, but white pokes at black shape with 3 and easily connects with 5 to 7.
If black tries to fight with 4 instead of connecting in the previous diagram, then white plays the move to 7 and capture the black stone. Black has to play 6 to avoid a total collapse of his shape.
In many cases, to avoid the sequences shown before, black should answer A with B.