White to play in the upper left. Revert to the usual practice? Or divert and gain? How and why?
Was black's last move a sensible move or just a mere trick play?
What will be the relation of a hane at the head of two stones to the next white move?

Let us answer these questions to achieve great knowledge in go, happiness in live and a prosperous future.

(My dear friend T. asked me, do you know the true meaning of your white move at E16. I was at a loss and took a deeper look. And I discoverd my friend's handtalk did not dig to the ground yet.)

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X B . . . . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

example pro game to explore the sequence in the upper left
Tan Xiao, 9p - Kang Dongyun, 9p, W+R (Komi 6.5)
24th LG Cup, round 1, 2019-05-27

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 2 . . . . . . . . . . . . . |
$$ | . . X X X 1 4 . . . . . . O . . . . . |
$$ | . . O O O 5 6 . . , . . . . . X . . . |
$$ | . . . . . . 7 . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 3 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

- and sente
Is your hane at the head of two stones?

Do you like to play at a or b? And why?

Hint:

Jump is a move I first saw Elf liking a while ago, and LZ likes it too sometimes now. It's particularly good in the very early opening when you want sente and to lessen the severity of the black follow-up after you tenuki in relation to the 3 stone wall.

The normal sequence is to 6 and then white tenukis, I put a few ideas for 7. Allowing black the hane at a would get a telling off from teachers of old, but the idea is although that hane at head of 2 is locally a very nice point for black, it's kinda slow at this stage AND it has little effect on the wall of now 4 stones up to 3.

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . 4 6 . . . . . . . . . . . |
$$ | . . X X B 2 1 5 a . . . . O . . 7 . . |
$$ | . . O O O 3 . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 7 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . 7 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

e.g. if black tries to "punish" white for allowing this locally bad shape then what? Note that white's 3-3 at top right results in a strong stone at 5 so the top is small for black. White merrily tenukis again and again. White's left side isn't under much attack yet.

Click Here To Show Diagram Code

[go]$$Wc black punsihes, or does he?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . X X . . . . 5 . . . . . . |
$$ | . . X X X X O O 6 . . . . O . 3 1 . . |
$$ | . . O O O O 8 . . , . . . . 4 X 2 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . 7 . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . 9 . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Compare to if hane (imagine same top right sequence)

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 2 . . . . . . 7 . . . . . . |
$$ | . . X X X 1 . . . . . . . O . 5 3 . . |
$$ | . . O O O . . . . , . . . . 6 X 4 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black has 2 normal local choices, atari and descend

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X . . . . . . O . . . . . . |
$$ | . 3 X X X O 1 . . . . . . O . O O . . |
$$ | . . O O O 2 . . . , . . . . X X 4 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

and cut and fight. This is normally a bit of an overplay without a black support stone on the left around a-c, tohugh if black plays there white may extend at 2 or hane at b17 and start some joseki to settle the shape there to avoid that fight that's now pleasant for black.

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X 3 . . . . . O . . . . . . |
$$ | . . X X X O 2 4 . . . . . O . O O . . |
$$ | . . O O O 1 . . . , . . . . X X 4 . . |
$$ | . . . . . 5 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . c . . . . . . . . . . . . . . . . |
$$ | . . . b . . . . . . . . . . . . . . . |
$$ | . . . a . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X a b . . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

After the white play at a, it is difficult for white to endure the pain of black H17 (Hane at the head of two stones.) White should extend once more at 5. It is now black's privilige to play elsewhere.

Click Here To Show Diagram Code

[go]$$Wc black to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 2 4 . . . . . . . . . . . . |
$$ | . . X X X 1 3 5 . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

After the white play at b, white can endure the hane at the head of two stones and play elsewhere himself.

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . 4 6 . . . . . . . . . . . |
$$ | . . X X X 2 1 5 . . . . . O . . . . . |
$$ | . . O O O 3 . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black should probably consider to play at F18 instead of E17 in the first place. But if E17 is good enough for top pros, we could also choose to consider it just as a matter of style. Especially as long as most of our opponents answer black E17 with white F17.

Click Here To Show Diagram Code

[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . B . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

I am glad the question by my friend helped me to add the knights move at b in the previous post to my repertoire and to sharpen my view on the hane at the head of two stones in relation to 3-3 invasion josekis.

FWIW, here is my first choice.

Click Here To Show Diagram Code

[go]$$Wc white to play
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X B . . . . . . . . O . . . . . |
$$ | . . O O O 1 . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The idea is to take sente, leaving no aji behind.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Frankly, I'm still rather partial to the old 3-3 variation, that I think most old masters would play if their opponent was insolent enough to invade 3-3.

Click Here To Show Diagram Code

[go]$$Wc Diagram 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 2 4 6 . . . . . . . . . . . . |
$$ | . . X X 1 3 5 7 . . . . . O . . . . . |
$$ | . . O O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Compare to one of the suggested variations after extending:

Click Here To Show Diagram Code

[go]$$Wc Diagram 2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 2 4 . . . . . . . . . . . . |
$$ | . . X X X 1 3 5 . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

What's the difference between these two variations? In Diagram 1, B has one less point, if nothing crazy happens, and the cutting points are shifted to the left. I think that shift slightly favors W - all B will really do against W's cut in either case is peep at it. Frankly I don't see any important difference to B having a peep on the fifth and sixth lines. B's cut being to the left means that W's descent or hane at B17 ought to be worth a little more in Diagram 1 than in Diagram 2, as far as I see. So I think Diagram 1 should be more than a point better than Diagram 2 for white.

My conclusion is that if you would play the variation in Diagram 2, you probably wanted a different variation and were persuaded otherwise after some tenuki midjoseki. Maybe that justifies the variation where you allow hane at the head of two stones? I think if I were white here, I would have played the old style variation, for whatever that's worth.

Definitly the differences are small. (KataGo about 1.5 points, Elf 56% versus 50%, Lizzie 60% versus 54%).

But all the bots agree on the trend.

Take care of the point and the game will take care of itself.
I recommended this continuation (of the starting position in the original post) for white (like in the actual Tan Xiao, 9p - Kang Dongyun, 9p game):

("recommended"
as in: this is a nice way to play, you probably did not consider yet
not as in: THIS IS THE ONLY WAY!!!!!!)

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . X X . . . . . . . . . . . |
$$ | . . X X X X O O . . . . . O . . . . . |
$$ | . . O O O O . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The key point is that white really strongly doesn't want to have to connect against the peep (inefficient) and would like to be able to resist, and that's a lot easier when you have a wall of 3 stones than 2.

It's too early, but say black peeped now and white tenukid (just to illustrate abstract shape difference). After cut of 3 the 2 stones are in more trouble...

Click Here To Show Diagram Code

[go]$$Bc Diagram 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X X X . . . . . . . . . . . . |
$$ | . . X X O O O O . . . . . O . . . . . |
$$ | . . O O 3 . . . . , . . . . . X . . . |
$$ | . . . . 1 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . 2 . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

...than with 3 stones.

Click Here To Show Diagram Code

[go]$$Bc Diagram 2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X . . . . . . . . . . . . |
$$ | . . X X X O O O . . . . . O . . . . . |
$$ | . . O O O 3 . . . , . . . . . X . . . |
$$ | . . . . . 1 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Now the white descent is fairly sente, so white can resist with this kind of idea to avoid a dame connection. Even so, because 4 is on the 3rd line black can later consider moves like a or b to push white down whilst making some sabaki in the centre, and white is only get 3rd line territory on the left side. (4 could also be on 4th line and leaves different aji).

Click Here To Show Diagram Code

[go]$$Bc Diagram 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X X X . . . . . . . . . . . . |
$$ | . 3 X X O O O O . . . . . O . . . . . |
$$ | . 2 O O . . . . . , . . . . . X . . . |
$$ | . . . . 1 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 b . . . . . . . . . . . . . . . |
$$ | . . . a . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

With the wall of 3 it's the hane and hanging that's the usual kikashi, and then white doesn't even need to extend on the side but could tenuki or gobble up the impetuous peep with a move like 6.

Click Here To Show Diagram Code

[go]$$Bc Diagram 2
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 3 . . . X X . . . . . . . . . . . . |
$$ | 5 2 X X X O O O . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . 4 . . . 1 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . 6 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Also the 5th line peep is a better shape follow up from a 4th line invasion on the left side, which is a more reasonable game flow to lead to the peep. Even now white can consider resistances, but black's moves are a large knight apart which is not so easy to cut without having some shape problems for white too.

Click Here To Show Diagram Code

[go]$$Bc Diagram 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X X X . . . . . . . . . . . . |
$$ | . . X X O O O O . . . . . O . . . . . |
$$ | . . O O . . . . . , . . . . . X . . . |
$$ | . . . . 3 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 1 . 2 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Compare to with the wall of 3, now the 6th line peep is less connected so black's fighting shape is worse.

Click Here To Show Diagram Code

[go]$$Bc Diagram 1
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . X X . . . . . . . . . . . . |
$$ | . . X X X O O O . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . 3 . . . . . . . . . . . . . |
$$ | . . . . 4 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 1 . 2 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

For a single game, 1.5 pts. is small, for a single move, it is large.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Agreed - but also the three other stones on the top side are considerably weaker with Diagram 2 than Diagram 1. I've found it much easier to play a consistent fight on the left when I have the extra stone on top. Yes, for all the reasons you pointed out the left is definitely weaker - but I can still take reasonable shape, and the top has an full extra, reasonably placed stone. Due to not having to worry about the weakness on top, I still feel poised to play 4 from your variation higher.

Click Here To Show Diagram Code

[go]$$Bc The circled W stones are not much of a worry.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X X X . . . . . . . . . . . . |
$$ | . 3 X X W W W W . . . . . O . . . . . |
$$ | . 2 O O . . . . . , . . . . . X . . . |
$$ | . . . . 1 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 4 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The fourth line relation to the 5th line peep is usually a small benefit, but after further progress in the fight the 6th line peep will at least threaten to become a good shape anyway. It is typically a little less clean for B to use the 6th line peep, with worse flow since it's unable to pose immediate questions, but I think not nearly as bad as the example diagrams look. In this particular case, my AI quite reasonably suggests that if B jumps in to the old-variation moyo B should start on the fifth line anyway, so I don't see how the 4th line relation is that relevant here.

To clarify - newer AI prefer the new (rightshifted) variation by over a point, and by 6%? The old LeelaZero I haven't gotten around to upgrading has both variation's evaluation rounding to 52%.

Perhaps my mistake is that I'm undervaluing the left side of the board - since a fight is expected to immediately break there, it does make sense that every little immediate strength advantage is worth its weight in gold. But is such a small thing really so exaggerated? It still feels counter intuitive to give up a point and help B strengthen a small weakness just to shift the outside strength balance an inch into W's favor.

That's a fair point about the top stones being weaker in the modern joseki.

You say with the modern joseki white gives black an extra point, but is that actually true? the cutting point at e18 does give quite a lot of future fun things to do for white. There's the life and death and yose implications of the h18 turn, and also this ko. It wouldn't surprise me if the old-style diagram 1 black corner actually ended up with more points on average, maybe KataGo ownership predictions can help?

Click Here To Show Diagram Code

[go]$$Bc Diagram 2
$$ ---------------------------------------
$$ | . 6 . . . . . . . . . . . . . . . . . |
$$ | . 3 4 5 . X X . . . . . . . . . . . . |
$$ | . 2 X X X O O O . . . . . O . . . . . |
$$ | . . O O O . . . . , . . . . . X . . . |
$$ | . . . . . 1 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . O . O . . . . . . . . . . . . . . |
$$ | . . X O O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . , . . . . . X . . . |
$$ | . . . X . X . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]