Episode 11 - San-san part1
Hi everybody.
Today we would like to give you some insight into the main weakness of a hoshi stone, the san-san point.
We will show you what can happen when white invades here, and will include some tricky variations.
Truth be told invading a hoshi stone on san-san is usually done when the opponent already has other stones around.
Let's first have a look at an example.
This is a position of a professional game between Hu Yaoyu and Wang Lu played in 2009.
Black just played B12, and is building a framework at the top.
You are white, Wang Lu, and about to make your move.
Where would you play?
Many of you might have thought about approaching the hoshi stone in the usual way.
But strangely enough the normal move is wrong.
The problem of the white approach with A is the many black stones that are around.
If black gets the chance to simply defend his corner, white has no space to make a base,
and will have to run.
White makes a small group at the top
but he has another weak group in the center.
Black will try to split them and attack them simultaneously.
Instead in the game Wang Lu invades on san-san.
So how do you know when to simply approach a hoshi stone and when to invade on 3-3?
As a rule of thumb
you invade on san-san when your opponent has a double wing formation from his hoshi.
Like black 1 and 2.
This is the perfect example of a double wing formation.
When your opponent has this kind of formation be sure to play severe and strike at the center, the san-san.
The reason that this white invasion is so successful has everything to do with the large scale framework black is trying to build.
Since both black's moyo stones are equally as high and equally as far away from his hoshi, black has a tough decision to make.
Blocking at A or B is all the same.
Black would like to block at A & B at the same time, which of course is impossible.
If black blocks from one of the two sides, we can expect the following standard pattern:
This pattern is the most basic one when it comes to invading a hoshi stone.
Important about this sequence is that white took the corner in sente.
A lot of black's potential territory has been destroyed
and white still holds the iniative and can play tenuki.
Note the position of the stones at 1 and 2.
These two stones originally formed the double wing formation of black.
Is black still happy with their placement?
As much as 1 is helping black, it builds up territory on the side of his wall
it feels like it's standing a bit too close to black's strength.
On top of that, the stone at 2 looks slightly strange.
When white invades and black has only one high wing stretching from his hoshi, the marked stone, black won't hesitate.
Black has no other choice and blocks from this side to make his stones work together.
Like this we return to the same joseki position.
White still has sente. The main difference for black is the absence of a stone at A.
This result is better for black than the previous variation.
If white would play tenuki, would you still play here as black?
Like in the double wing formation?
...black could also choose to play further away from his strength
or try out other huge scale plans..
or simply leave the incredibly strong group at the top for what it is.
Since the top group is already strong it doesn't really need an extra stone.
Now that we've seen the main sequence where white destroys the corner in sente
let's have a look at some other possibilities.
When white plays this hane black does not have to extend
black can also play the severe double hane.
This black hane can be very powerful.
white has two possible responses.
Going for the right side with 1
or starting a strong counter attack and aiming for the top with 2
This atari is the easiest of the two and leads to a straight forward result.
White takes the black stone and sacrifices his corner.
this result is locally even
White gets a ponnuki shape on the outside and keeps sente.
Black gets a very big corner.
But the two white captured stones still have a lot of aji
This aji makes it easier for white to invade at the top
For example, around A, let me show you.
This leaves a lot of aji moves on the top side.
But even if white does not get the opportunity to use the aji around A..
this exchange still leaves him some benefits in the corner.
This hane for white is big endgame.
What is the correct answer for black?
This is wrong.
It gives white the opportunity to play this in the late stages of end-game.
Instead this is the correct move.
If white is not interested in the right side, but in the top instead..
The hane at 2 is interesting
Black has to block, it's the only move.
It looks like white is confined to the corner but he has this powerful tesuji
The proper answer for black.
Black has many other choices, but they are usually wrong.
If you are interested in these other possibilities
please have a look at the bonus section of this episode where we include more variations
Another trade is the result.
Black takes the corner, and white is happy with the top.
Black can also try something different here, this tricky cut.
It looks like a crazy over play, but it's actually a good probe.
However black needs a favorable ladder for this to work.
If white has the ladder he can extend on the second line.
This is the ladder
If the ladder is good for white, this is of course a great result for him.
If white has the ladder the best black can do is to play atari from the other side
like so
This result is slightly better for white.
So black really needs the ladder to play this tricky cut.
So if black has the ladder, white cannot extend at A.
Capturing the black stone is one possibility.
In the first and most basic variation of this episode, white also took the corner, but was not completely surrounded.
Black still had an open skirt on the right side.
But now the marked stone blocks white.
White is completely sealed in.
Also A is big endgame and sente for black.
If white does not respond black can make a big ko in the corner.
Black can take this ko first, so white has to find the first ko threat
This is the second option for white.
See the bonus tab for some games with this variation.
Today we showed you most of the joseki patterns that come forth from this black hane.
Next week we will continue to explain the san-san invasion of a hoshi stone
and will surprise you with other tactics that black can apply.
See you then!