The L+2 group
Hi everybody, today we would like to continue the san-san series..
..by showing you the ins and outs of a corner group that comes forth from the last variation that we showed in episode 12.
Black has an ogeima stretching from his hoshi stone.
White invades on 3-3.
We arrive to this position.
The white group is alive.
It is one of the most basic corner groups that you will encounter in your go games and it occurs frequently.
It is called the L+2 group.
Since the shape resembles the letter L, which has one extra stone on both sides.
At this moment white has two options to defend his corner.
This is the normal move, which is played most often by professionals.
It is usually best for endgame.
Instead of the solid connection white can also play a hanging connection.
This move is usually wrong, because of a black endgame tesuji.
First let's point out that this descend is sente.
White has to respond to this move or else his group will die.
This is the way to kill, this move is cool to remember.
Another tesuji, white can't make an eye here, black will simply atari, leaving white with only one eye.
So white has to defend.
The proper response, white lives.
Let's focus on endgame counting.
White has six points in the corner.
It is not sure that point number 6 will be white's territory, but let's count it for the sake of comparison.
So what about that endgame tesuji?
In the late stages of endgame black can use this vital point to take away some territory of white.
White has three point of territory and sente.
Black and white both captured one stone.
This is even, so we leave this out.
Why not take the black stone instead, isn't that more points?
Yes it's 1 and a half points bigger, but it also loses sente.
White has captured two black stones and has three points of territory
making five points in total.
Black has the possibility of taking the ko, so we count this as minus half a point for white giving him 4 and a half points.
In the previous variation white had three points and sente.
Black has sente now.
To summarize white can choose to take sente or to take one and a half points in gote.
With the black endgame tesuji, white's hanging connection seems wrong.
So when is it a good move?
In certain special situations the hanging connection, or tiger's mouth is best.
This is one of them.
If white would play the usual move, it would actually be a mistake here.
This black descend is the key point of the situation.
It is sente against the L+2 group and it also threatens to set blacks two seemingly captured stones in motion.
If white defends his corner, black has a very sneaky tesuji up his sleeve.
Black connects all his stones, and suddenly white's group becomes weak.
A great result for black!
If white defends the other side..
black has aji in the corner, and can make a ko.
In such a tsume-go situation the first move that comes to mind is the black extension.
However this does not work here.
White has one eye in the corner and A and B are miai.
Two eyes in total.
Instead black plays a kosumi to make a ko shape, the correct move.
If white tries to kill the black stones, he actually dies himself.
White is confronted with a lack of liberties and can't seperate the black stones.
White can't kill the black stones and has to try to make two eyes.
This leads to a ko.
White can take the ko first, but still this is a big success for black.
What a master player!
So, when white plays the more common connection, black will profit.
Here a hanging connection instead would be better.
The correct move, in this shape black A is not sente anymore.
Now blacks connection fails.
White can seperate.
To conclude:
This solid connection is best when it comes to territory.
But remember that this descend is sente for black.
When white does not want A to be sente, he can play here.
But again remember now the extension on the other side is sente.
One final tip in relation to whites solid connection.
Apart from the special move that black has at A, more straightforward ones like B and C are also sente.
When black plays one of the two hanes..
you can defend your corner with a stylish jump.
When black plays the other hane at C, here the stylish jump also works..
but this is the clearest shape in this position.
Thanks for watching and see you next time!