Why does White atari at this exact moment? Why not block at A? And why doesn’t Black connect? So many questions:)
This shape stems from one of the 1000 new 3-3 invasion variations.
Though if you’ve never seen this shape before, I don’t think you’d care about the following.
First of all, when White plays atari, Black cannot connect at 2, for White 3 works now.
Because after the cut 4, White gets the atari 7 in sente, so Black cannot capture White on either side. Black is now dead inside.
Black can only try the semeai with the corner. This yields a ko, but there are no threats (and White has one local threat), so Black dies again. It’s good for White because White invaded in Black’s corner and kills Black.
As for why White should play A instead of blocking 1 directly, it’s because Black can peep 2 and clamp 4. (If White comes back at A now, White would rather not have exchanged 1-4.)
So White 4 tries to disconnect Black, but now Black can push one more time at 9, aiming at A and the geta B.
White could hane at 10 to threaten the two marked super-vital cutting stones, but…
Now Black responds with 11 and 13. A and B are still miai, so White is toast.
This explains why White cuts at 1 and Black doesn’t answer. Apparently someone invented the keima 2 to make White heavy…
And Black somehow ends up getting out at 6, completely ignoring the well-being of the two marked stones. Unfortunately, the commentator Wang Yao 6p in this WeiqiTV video didn’t show the further continuation. But these variations still answered some questions that came up a while ago and stumped me.