I think you're thinking about it all wrong. Just forget the entire concept of shape and look for
good moves. Shape is an emergent set of behaviours in that certain layouts of stones turn out to be good moves more often than others. In principle, we don't play shapes because they're shapes, we play good moves and happen to notice the common shapes afterwards.
Of course, in real games shape turns out to be an important topic because the statistics turn out to be an excellent heuristic by which to adjust our reading. A strong player's eyes in a given situation will probably first be drawn to shape points, which are shape points specifically because he's played hundreds of games and recognises that they were often important.
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It seems that in the first half of the game, shape is more to do with the density of stones, rather than their exact arrangement? For example, .
There are 2 examples of white making kosumis on the second line towards the corner (moves and ), which were described as good shape and approaching the corner, but which were easily blocked by black. The resulting arrangement I understood to be generally better for black:
Of course shape is important, but I think you're grasping too rigidly define something that isn't generally viewed that way and (I'd even perhaps say) isn't useful to view that way.
As above, lets ignore the entire idea of shape when analysing these kosumis and analyse the board purely in the context of good moves. In both cases, black threatens to cut off one of white's stones and white has decided he wants to prevent that by connecting out somehow. There are several ways to connect:
- Click Here To Show Diagram Code
[go]$$W
$$ . . O . .
$$ . d e . .
$$ . c f X .
$$ . b O . .
$$ . a . X .
$$ . . X . .
$$ . . . . .[/go]
Any of a,b,c,d,e,f will connect white's stones. Each have advantages and disadvantages. f, for instance, doesn't impact the corner but does damage black's stone slightly. e has more effect higher up the board but again doesn't impact the corner.
Now, in the context of the actual board position white decides that he's sufficiently strong on the left that he doesn't risk leaving himself thin and so doesn't need a move up there like e, d or f. On the other hand, he doesn't feel strong enough to push and cut so he'll just try to connect. He could play b, but why hold back when a also connects but also threatens a jump into the corner? Therefore, he plays a. This gives the maximum payoff per connectedness; if black tenukis, white can jump into the corner.
Now if we play lots of games and observe lots of results,
then we can begin to make some observations about shape. We can see that
in situations like this (where defining 'like' is an exercise in itself) white's best shape is a because it simply has the best followups - either being sente or allowing the best jump into the corner. It's a little weaker further up the left, if the board was different then maybe white would have a different best shape.
Your attempts to categorise shapes seem...well, too naive. Even with the strongest shape proclamations we can make, like empty triangles being bad, it's absolutely trivial to find many many situations in everyday real games where the shape is actually good. That's because shape is something far deeper than being just good or bad, and when making judgements based on shape you have to think about the constituent factors. For instance, in the example above white's kosumi is good shape because it gives the best payoff in this situation. More, situations like this are common enough for the outside kosumi to be a recognisable good shape for trying to get a good payoff. However, there are also lots of situations you might think are similar but are different enough for a different move to be best, and understanding shape must involve understanding this.
This is all very long winded, but it all still comes down in the end to playing shape being the same as playing the best move. Frankly, at your level I think by far the best exercise is to play lots of games (plus reviews) and let your understanding of shape develop by actually getting the statistical experience you need to make the judgements. As you read many different situations, good shapes naturally reveal themselves and become a part of your reading patterns. If you try to force a false understanding, you'll just end up playing bad moves by misunderstanding what a shape means. Of course studying shape may be important, but I think the real meaning of that will be clearer with more experience.