Large avalanche - turn inward
Its main idea is that if White answers with here, Black next turns at , and after some standard variation of the outward turn has been played, the exchange of for will have given Black two free points compared to playing at directly. Of course, for a professional player to lose two points without any compensation is unthinkable, so this in general is not played.
To avoid the variations as mentioned above, White exchanges for before playing at . The moves to invariably follow.
is joseki, but is a mistake. , making miai of and , brings White to an uncomfortable position. With correct play, White will manage to save her three stones and live, but while White is only making two eyes, Black will get superb influence.
Although there have been attempts with different moves, the sequence from to here is by far the most common.
The main variation of the sequence above, is the one where is played on the top as shown here (sometimes is played at already, followed by and ). White accepts that there is a chance of losing her three stones at the left, and takes influence at the top instead. Black next can choose among a, b and c and others; I will give one possible continuation for each.
is forced, after which is one possibility. proposes an exchange (see the next diagram) with each player capturing some stones, but Black refuses, and fighting will continue on the left side. Black has some very bad aji in the corner though, White being able to set up an approach ko here with White a.
is the most common variation, after which the variation to is forced. and form the most common continuation. After this, the fighting is not over, but there are no standard variations any more.
After the cut with , Black captures two stones. Black has taken about 20 points of profit in the corner; White will have to make up for that through her advantage in the center fight.
For Black, a variation that has been tried is this instead of in the last diagram of the main variation. is the key move here. It creates the approach ko (also mentioned above) of White a, which makes this variation problematic for Black.
After the main line, Black can play a, allowing White to extend along the left side, or Black b, preparing to play on the left side himself, or he can play tenuki, probably making preparations to sacrifice his three stones. In the corner, the three stones have been captured, but there is still some important aji left.
If White plays and , Black should not play immediately, because in that case White will play . This creates an approach ko, which in this position is a very good result for White. Instead, Black should exchange for first, then play . Now White is captured because of double ko. However, this also means that White has an unlimited source of ko threats here, so she will win any ko worth less than about 30 points anywhere on the board.
After , she again threatens an approach ko, but Black can avoid it again, this time by playing at . However, after these moves, is almost sente, because a follow-up at a threatens to connect underneath. Having the possibility to play in sente gives White an advantage in any fighting that might break out at the top.
is the most common continuation for Black. White usually answers by making a base for her left-side group with . The moves to may be considered the standard continuation of the joseki. Instead of , White a-Black b is also possible. For the variation where White plays at c, I refer to Ishida.
denotes some special strategy. is a natural answer: White plays the point that Black neglected to play.
is a more aggressive move. Black intends to build up strength here, then make a checking extension on the left side. The tough answer at is the most common answer, but white also sometimes plays a, or plays her sente in the corner, starting with b, first. Black builds a wall with to , then attacks with . If he does not want to make White so strong this way, Black might also play at instead of or .
White attaches at and pulls back. After , White can attack with moves like a or b, and both players will go on towards the centre.
Someone commented that the joseki then continues:
White wins in the corner, but acc to the commentator it all depends on a ladder at . I do not yet see it.
fractic: If Black does not have the ladder he now has to play a. He'll get the three white stones but White captures Black's lump with b. If Black does have the ladder he can connect on c and since the ladder starting with b no longer works White is devestated.