This game is GoGoD 1600-00-00n, between Honinbo Sansa (W) and Rigen. OC, today's pros are stronger, in no small part because we have learned from their mistakes.

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[go]$$Bcm37 Textbook shape
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . O . . . . |
$$ | . . . W . . 1 . . X . . . . O X . . . |
$$ | . . . , . . . . . , . . . O X X X . . |
$$ | . . a 2 . . . . . . . . . 4 O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . 3 W . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . O . . . . . . . . . . . . |
$$ | . . O . . X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

These were the days before corners, sides, center, which explains why Sansa had not enclosed the top left corner earlier. But not only made a base, it threatened to invade White's thin corner position at a. So White protected it with which, with the stones made what would later be a textbook shape in the corner. ( might also have been at a.) intruded into the corner, a mistake that lost 17½% to par by Elf's reckoning. Then White made the solid connection, .

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[go]$$Bcm39 Variation for
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . 6 . . . O . . . . |
$$ | . . . O . . X . . X . . . . O X . . . |
$$ | . . . , . . . . . , . . 2 O X X X . . |
$$ | . . . O . . . . . . . . 4 1 W 5 . . . |
$$ | . . . . . . . . . . . . . . 3 . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X . O . . . . . . . . . . . . |
$$ | . . O . . X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

cuts White in two in the top right, then captures the stone. supports his group and threatens the Black base. The White stones in the upper right side have been weakened.

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[go]$$Wcm38 Key point
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . O 2 . . . |
$$ | . . . O . . X . . X . c . . O X . . . |
$$ | . . . , . . . . . , . . . O X X X . . |
$$ | . . a b . . . . . . . . . 1 O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . , . . . . . , O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . X 3 O . . . . . . . . . . . . |
$$ | . . O . 4 X O . . . . . . . . . X . . |
$$ | . . X . X O . . . . . . . . . . . . . |
$$ | . . X , X O . . . , . . . . . , O . . |
$$ | . . X O O . . O . X . . X . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The solid connection, , is the key point for White. It radiates strength towards the right side, the top side, and the center, and weakens Black's corner. After White takes sente in the bottom left quadrant, but a, b, or c would also be good.

Speculatively:
Current position:
1. B12 seems natural, even if B responds, W jumps and there is still some aji with F9 eyeing C6 aji.
2. O14 is solid, but B at C15 is too big.

Opp to play
1. C15 to just live in corner is very powerful
2. O15 also very big.

Past:
1. B has large lower left and W doesn't have much to make up for it. Though R8 is fairly weak and so is upper right corner, they seem stable for now as W isn't that thick. W can probably build something in the centre but I don't know how. I like B a little, but there are several tense situations and I don't know how they will resolve.

Check:
1. not quite