Cap/discussion

version 7 of the main page (13th August 2006):

The cap is visualized in the following diagram. It can be seen as the counterpart of the one point jump.

Cap  

Alex Weldon: I believe it's a bit more specific than that, though. It's only boshi if you're playing with an one point jump relationship to your opponents stone, with your stone in the direction of the center. Right? Or is the term more general than I believed it to be?

John Fairbairn This is an interesting one because the Japanese never define it really. They exploit the fact that boushi is written as a Sino-Japanese word and define it with a pure Japanese word meaning the same thing. A bit like cap: see hat. Hat: see cap. But I can say that a two-space cap is also possible.

Why not say cap? After all it's not boshi like hoshi, it's boushi.

Charles Matthews A cap should block the opponent's natural line of advance towards the centre. In the various counter-pincer strategies the key moment may come when you do that. But here 'towards the centre' doesn't mean towards tengen, necessarily. It means the opponent in the running fight has to turn though ninety degrees, or else make a soft-hearted shape. This would be worth a further page on cap as attacking play?.

Cap as a reduction move  

Here the cap reduces the moyo formed by the black stones. If Black were allowed to play at 1, his moyo would be perfected.

Cap as an attacking move  

Here the cap blocks off White's natural escape to the center. The purpose can be twofold: make territory at the top while White is fleeing along dame points and/or create thickness towards the center.

Authors:
Dieter Verhofstadt

end version 7

new discussion:

Chris Hayashida: This is nit-picking, but I think the diagrams should be turned 180 degrees. It would make more sense, at least compared to the example diagram. Also, most people don't wear caps on their feet. :)

xela: OK, I've inverted one diagram but not the other. I think people need to get used to mentally inverting/rotation go positions. That's why, on the main page (not here), I've linked the word "above" to Up and down.

Question:

erikpan: Since this play isn't mentioned anywhere, I'd assume it was a bad move, but I had this 'psuedo-cap' played on me (as white) recently:

19x19 diagram  

I realise this move (w1) on the 3rd line was probably a mistake; I suddenly became worried I had none of the corners (although I had pushed back quite far) and dived for some territory in desperation, but I didn't expect this very close cap and wasn't sure how to respond. My immediate thoughts were the circled points, or tengen, since I had the beginnings of walls closing in all the corners; although this is inconsistent since I played 1 for territory and should follow that up. Any thoughts? Thanks :)