• a, 4-4 Point 3-3 Invasion, Double Hane, Counter Hane, Connect - (joseki) (common) (intermediate) (AI favorite)
• b, 4-4 Point 3-3 Invasion, Double Hane, Counter Hane, Atari - (situational) (advanced)

Overview of Joseki

If Black plays the double hane, Black has to be prepared for this . White intends to give up the corner in exchange for a position on the top. In an emergency, however, instead of Black may play at a; the likely outcome is that he gives up a bit more territory in the corner in order to maintain his outside wall.

is now almost always regarded as a mistake by AI. Previously, it was regarded as a situational joseki, useful in cases where black has staked everything on making a big moyo at the top so that does more damage to the moyo than it loses in the corner. But recent analysis seems to indicate that the damage is hardly ever worth giving away a larger corner (see https://lifein19x19.com/viewtopic.php?f=15&t=17352).

Incidentally, this variation has been coined "switcheroo ponnuki" by Uberdude.

After in the previous diagram, is the joseki move, reaffirming the unity of the black stones. After , White can secure a base with a move like a or play tenuki.

With in place, Black can resist. White can live - very small in the corner or belatedly take the other ponnuki starting at a. However this is worse than taking the other ponnuki directly.

Discussion

The presence of extra stones

In White's counter hane variation, this atari play is recognised as joseki, but is highly sensitive to stones on the upper side, for example at a or b in the following diagram.

These plays occur in pro games. When Black plays , White will eventually have to live at e. Before that White has a chance of pulling out the marked stone with White c, Black d and White continuing on the third line for a while. The books teach that this is good for White if Black has a stone at b, but poor if Black has a stone at a.

If White lives immediately at e and Black tidies up by capturing at c, Black will be thick anyway (possibly slightly overconcentrated).

There's an early example in Chapter 1 of Beauty and the Beast.

[4] Double Hane: As with so many novelties, it has been seen much earlier. In the case of this joseki, Kajiwara Takeo played it as early as 1958.

References

• [1] Frequency statistics were obtained from Waltheri's Go Pattern Search using the full database restrained to a local search (accessed September 2022).