4-4 point low approach one-space low pincer, low double approach
The double approach is an alternative here for White to invading the corner at a.
The presence of makes a big difference to later play.
The answer at is now standard.
Black at a is the main other choice; Black at b is occasionally played.
Now White's main option is to invade with . White also can try playing out at a first, but the timing involved isn't easy to grasp.
After , Black has to choose on which side to block. In the past few years both the circle point and square point have been common in pro games.
After and , is an essential bulge point, and too good to allow to the opponent.
If Black blocks at , the variation to is to be expected.
After this, Black has to deal with the white stone on the left; is one possibility. White is aiming at the cut at a, and might well play there immediately.
The joseki is slightly off, which professional players might translate into an immediate win or loss.
Alex Weldon: Slightly off in whose favour?
Charles The evidence from recent pro games is that Black is still experimenting with (also played at a or the circled point). Therefore assume Black is somewhat dissatisified here.
The purpose of is to protect against the hane at ; White is not really alive yet, so she plays at to live in sente.
A second possibility for White is the hane at followed by . Now is the simplest answer. Black has sente. This is a good joseki for White if Black is trying to make a framework on the left.
We will show one continuation, from a professional game. creates aji.
Black gets a large wall, White the corner territory. White has the aji of pulling out? at a.
White could also invade at the 3-3 point after the exchange of for . If Black answers at or some such point, we get a transposition to the joseki above.
Alternatively, Black can answer by blocking on the outside with . After , White's territory is bigger, but so is Black's thickness. In the rare case that Black can successfully challenge White to a ko fight, White can omit the - exchange.
The attachment on the other side with is rare. With this move Black is trying to build a wall facing the top, but he runs a serious risk that the original pincer (the marked stone) will turn out to be too close to it.
Here is one possible variation. Other moves, like at c or , are even more rare with this pincer.