Joseki: Sansan invasion, response never seen before

[RobertJasiek]

The 1d pupil would not make such mistakes. He has knowledge gaps but is not stupid and would not make the kind of ridiculous mistakes you describe.

[Uberdude]

About the net vs firmer atari, your pupil is in good company at making that mistake (I agree it's a mistake), I remember recently reading a pro game commentary in which the pro made the same firm atari, when the net was better. But the small additional territory is not the only difference, indeed I think it is not the most important one here, and it certainly wasn't in the pro game. It is the fact that with the atari a becomes a sente peep for black which can be useful for the black group on the lower side. The pro game was, if memory serves correctly, remarkably similar though I think the black group was once one space to the left (oh the irony!) and was in fact under more pressure than your game, so that additional sente peep was a big help in settling that group.

$$Wc Peep with firm atari
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . X O O O . . . . . . . . . . . . . |
$$ | . . X O X . . . . , . . . . . , . . . |
$$ | . X O . O . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . O . . 1 . a . . X . . . . . . . . . |
$$ | . X O O X . . . . X O . . . . O . . . |
$$ | . X X X O O O . . X . . X . O . . . . |
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Wc Peep with firm atari
$$ | . . X X X X . . . . . . . . . . . . . |
$$ | . . X O O O . . . . . . . . . . . . . |
$$ | . . X O X . . . . , . . . . . , . . . |
$$ | . X O . O . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . O . . 1 . a . . X . . . . . . . . . |
$$ | . X O O X . . . . X O . . . . O . . . |
$$ | . X X X O O O . . X . . X . O . . . . |
$$ | . . . X X O . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

[tapir]

Maybe you should teach White how to avoid getting so overconcentrated instead of trying to optimize territory in a completely overconcentrated position. In fact, White could in this case probably play at something like ''a'' (in the diagram of Uberdude, jump out) outright not even capturing the Black stone directly at all.

[RobertJasiek]

Maybe you should teach White how to avoid getting so overconcentrated

Unless a lesson's teaching topics emphasise something else, there is not a "maybe you should" but there is an "of course I do". Since the topic here has emphasised something else (correct move when the position shown is already given), I have not mentioned it in this thread before.

[RobertJasiek]

It is the fact that with the atari a becomes a sente peep for black which can be useful for the black group on the lower side.

In case of the joseki atari, Black always has such a peep available and would often use it when a group of his needs assistance. In case of the net, Black has other aji exploitation moves but in the game here the interesting ones are not so easily available. So currently the net captures more firmly than the atari, and this would even agree to Kageyama's idea.

Another aspect is territory efficiency (territory per invested stones).