In this game Shusaku-Ito Matsujiro from 1844, Black places more importance on the fight in the lower right than on extending on the upper side, after the checking extension White 2. Black 3 is, according to normal thinking, played at a.
Black continues with a framework plan at the bottom, rather than running out with b. How does one evaluate this?
It seems that this makes a trade-off: some gain for White on the first point, a gain for Black on the second point.