The game is GoGoD 1925-01-00a, Honinbo Shusai Meijin (W) vs. Nakagawa Kamesaburo II, 8 dan.

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[go]$$Bcm21 Actual game
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . O . . . . |
$$ | . . . , X . . . 2 , . . . . . , O O . |
$$ | . . O . . . . . . . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . a . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . O . O . . |
$$ | . . 1 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . X . . X . . |
$$ | . . X , X . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Nakamura played the checking extension, , and Shusai replied with . Both plays may be best with no komi, but Elf, assuming komi, reckons that loses 13% to par and loses 10½% to defending at a.

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[go]$$Wcm22 Mainline for
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . 9 5 3 O . . . . |
$$ | . . . , X . . . . , 6 7 4 2 . , O O . |
$$ | . . O . . . . . . . . 8 . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 1 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . O . O . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . b . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . X . . X . . |
$$ | . . X , X . . . . , . a . . . , . . . |
$$ | . . . . . . . . . . . . O . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

After , for Black plays the press on the top side to bolster his group in the top right quadrant. a and b are also playable, to bolster his group in the bottom right. b makes a base for either Black or White.

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[go]$$Bcm21 Press, then invade
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$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . a . . . . . . . |
$$ | . . . X . . . . . . . . 4 2 O . . . . |
$$ | . . . , X . . . . , . . 3 1 . , O O . |
$$ | . . O . . . . . . . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 5 . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . O , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . O . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . X . . X . . |
$$ | . . X , X . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Black presses in the top right and then invades on the left side without further preparation. could also be at a. Since the Black invasion complicates the game, you can see how it might be unattractive with no komi.

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[go]$$Wcm26 Invasion variation, continued
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . O O O . . . . |
$$ | . . . , X b . . . , . . X X . , O O . |
$$ | . . O . 1 2 . . . . . . . . . X X . . |
$$ | . . . . 3 7 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . B . . . . . . . . . . . . . . . . |
$$ | . . . 4 6 . . . . . . . . . X . X . . |
$$ | . . O 5 8 . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . O . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . a . . . . . . . . . . X . . X . . |
$$ | . . X , X . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . O . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The jump attachment, , runs out with a leaning attack against . White could also play the 3d line attachment at a to make a base for White in the bottom left. blocks Black, but could also be at a or b. After pushes into the center, plays the strong central turn.

The key difference between the two mainline variations is the invasion on the left side. Black gets in the press in the top right in either case. Black needs no further preparation for the invasion. The kosumi in the top left corner is preparation enough. (OC, we know that an invasion is possible without the kosumi, as well. ) In komi go the checking extension amounts to a losing sente.

Speculatively:
Current position:
1. Ooh, this is much trickier with all the weak groups. Neither shape has particularly weak shape though so perhaps more plays aren't too big a deal. B is a bit undercut at S15.
2. Of course the upper side stands out: the last open side, E16 is vulnerable to W H17; B K17 can help support the P11 group.
3. I wouldn't invade C12 when W C10 has so much space, can counterattack E16, and is ahead in the centre with N9.
4. C8 is very attractive but I feel slightly early as miai with J3
5. J3 is nice but conflicts slightly with moves like M4 as O5 seems too weak to me.
6. O3/R3 still look good to me. O3 seems to perhaps give up too much access when there is so much space with W G3.
7. R7 is big fighting eyespace point, though perhaps slightly inefficient.

Opp to play
1. I feel H17 is biggest to shore up the left side at the same time as building something at the top.
2. G3 looks nice, but I'm not completely sure W has enough advantage in the fight if B plays M4.

Past:
1. I feel I have to slightly prefer B in this position as I think N9 looks slow and C10 is not at a vital point. However, handling O5 requires some careful use of W's weak points.

Overall:
1. Difficult, but I'm tending towards liking M4 since I'd like to threaten the N9 group in the fight. However, I'm not sure B can really win the fight though when W plays N5 and cuts.
2. Otherwise, I want to see K17 or L17.

Check:
1. Got most of my ideas right, but missed the sharpest fight that ELF was angling for.