It's unclear to me how W can do that easily. For example:
- Click Here To Show Diagram Code
[go]$$Bm21
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . O . . . 5 . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . O . . . 1 . 4 . O O O . , X . . |
$$ | . . O . . X . . 3 2 . . X X . X . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ -----------------------------------------[/go]
The exachnage of 23 for 24 is usually crude. However, here it looks good since W becomes overconcentrated. Normally, the shape made by stones 22 and 24 is very strong. However, here W's group is too close for it be effective.
Then 25 grabs a nice point in the centre, and it should help to alleviate the impact of W's thickness.
Alternatively, W could try this:
- Click Here To Show Diagram Code
[go]$$Bm21
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . O . . . 1 . , . O O O . , X . . |
$$ | . . O . . X . . 3 5 . . X X . X . . . |
$$ | . . . X . . . 2 4 . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ -----------------------------------------[/go]
This could well be an overplay. I don't see how W can connect or cut after B 23 here. Even if W can achieve life, it is unlikely to be a good result. B will become thick, and already has a lot of territory.
As played, B will be very low on the lower side. For example:
- Click Here To Show Diagram Code
[go]$$Bm21
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . 8 . . 3 . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . . O . . . . . . . . . . . . O . . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . O . 6 . 4 . , . O O O . , X . . |
$$ | . . O . 7 X . 5 1 . . . X X . X . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ -----------------------------------------[/go]
The forcing moves at 24 and 26 are helpful in developing a scary central moyo.