Systematic Joseki 4-4 3-6 6-4 3-9
Summary - Strategy - Hoshi Low approach Ikken tobi Niken tobi
In beginners' books 4 is usually described as an error, leading to overconcentrated shape. However, things are not so clear, as White can still invade the corner at san-san.
I feel the invasion sequence should be included here.
unkx80: Sometimes the exchange of and
is not played. While the exchange makes White overconcentrated,
is indeed a very strong move towards the center.
Rich: There's some aji, but not enough to compensate. As long as black's stones remain fairly stable, it's an endgame play, not a corner invasion: Black keeps the corner. This, according to all professional opinion I've ever read, is not a joseki; it is why if white intends to play the marked stone, she should always play at the 4-2 point first.