I've been seeing the following shape lately in games. I feel like I should be able to kill the group, although I also wouldn't be surprised if I can't. Trying to figure out what the best way to attack white in this situation is. In the game, I attached at S7, and chased the group out.

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

The textbook, usually correct answer is the bump:

Click Here To Show Diagram Code

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

This forces a miai between 'a' and 'b'. If Black plays 'a', then 'b' by White ensures Black still doesn't have two eyes and almost cuts off R7. Black could save it with the clamp of S7 but it doesn't give Black additional eyespace and it saves in gote, so it's not a good choice. If Black plays 'b', then 'a' by White caps Black from creeping any higher up while also making sure Black doesn't have two eyes.