Standard opening 1
The following is a standard opening. It has been thoroughly investigated by Cho Hun Hyun and Lee Chang Ho and often occurs in Korean pro games of the '90s. We start with four corner star points.
Up until , this is a local joseki of the bottom left. Now White faces the decision where to move next.
is considered whole board joseki[1] after which Black patches up the weakness at a.
is considered mandatory, because a black move there would be sente for the threat at a). Black continues utilizing his thickness to play on the left and apply pressure on White's corner.
is a standard diagonal haengma to prevent being enclosed by a double keima. (Dieter ignores the exact reason for
).
White must respond at according to whole board joseki [2]. At
, the standard opening comes to an end, that is to say, professional players believe that no further research is paying off and this has found its way into standard (Korean) textbooks.
[1]
This gives quite a bit of cash? at the bottom left. However, after
, Black takes a global lead, or rather, the position is considered active? for Black. So,
is called a whole board joseki mistake.
[2]
White would like to resist Black's speedy play by punishing him for leaving the marked stone unattended, but Black sacrifices the stone and takes sente to play in the next diagram. This is again called active for Black. Hence
is a whole board joseki mistake.