(;
AB[fc][dr][fq][pp][pn][oc][ob][pc][pe][pd][oe][of][pg][ph][qh][oh][nh][mh][lh][jh][id][jc][lc]
AW[dp][cn][dd][cf][ie][if][le][lg][qb][pb][qc][qd][qf][pf][rg][og][ng][nf][pi][np][qn][pm][nc]
TR[pm]
C[Black's response to the marked play?

Source:
    "Go in the 21st Century"
    Yoo Chang-heok 9P vs. Yoda Norimoto 9P
    Commentary:  Go Seigen 9P
    American Go Journal, Vol. 31, No 2, pp. 16-17]
(;
B[on]
C[Go Seigen says that Black extending toward the center here is absolutely necessary.];
W[qo];B[op];W[rq]
C[White could take the big corner points, but ...];
B[jp]
C[... Black can now take this bottom point.  Black's stones in the center and at the bottom are all working together to give influence across the entire board.]
)
    (;
    B[qo]
    C[In the game, Yoo played here, which overvalues Black's profit in the lower right.];
    W[on];B[po];W[om];B[qm]
    C[Black follows the joseki with this big play.];
    W[ql];B[rn]
    (;
    W[rm]
    C[Now White is the one who blindly follows the joseki with this atari.];
    B[jp]
    C[In this game line, Black now has time to take the urgent point at the bottom.  Even after Black's right side mistake in direction, White is still behind on the whole board.]
    )
        (;
        W[jq]
        C[Instead, Go Seigen says that White must ignore the right side joseki to take the urgent bottom point.];
        B[rl]
        C[Black takes the big right side point, but ...];
        W[cq];B[hq];W[jo]
        C[... White not only takes the big lower left 3-3 point, but also settles the lower center group.  The board is now balanced and the game will be a long drawn-out game.]
        )
    )
)

