(;
AB[jb][ic][id][ie][if][kc][mc][md][nc][qc][ed][gd][ge][pd][be][ce][fe][ne][nf][ng][qe][of][pf][cg][hh][lh][mh][ni][nj][lj][pj][bk][ck][ek][bm][dm][dn][do][dp][dq][cn][mn][jp][np][nq][pq][pr][or][qr]
AW[hb][hc][ib][lb][lc][ld][dc][ec][fc][cd][fd][nd][rd][re][je][me][mf][mg][kf][qf][og][oh][pg][ph][kh][ki][nh][ci][ei][gi][hi][ii][qi][bl][cl][cm][bn][on][qn][co][cp][cq][cr][op][oq][pp][qq][rq]
PL[W]
C[White's response to the marked play?

Source:
7th Tengen, Kato Masao 9P(B) v. Kobayashi Koichi 9P
Go World #27, p. 25,  Spring 1982]
TR[bk]
(;
W[eg]
C[The only move in this game that Kobayashi regretted.];
B[ef];W[ch];B[fh]
C[Now Black's peep here and Black's next move reverse the flow of the game.];
W[fi];B[dl];W[am]
C[With the center dragon still insecure, White is unable to do anything about Black's lower moyo.];
B[kd];W[lg];B[jg];W[kg];B[bc];W[cb];B[dr];W[hl];B[qj];W[rc];B[in];W[kk];B[ml];W[de];B[df];W[bg];B[bd]
C[And next, Black should have connected here to guarantee life for this group.

In the game, Black made a mistake by playing elsewhere.  However, Black did still go on to win the game by a small margin.]
)
    (;
    W[ch]
    C[Instead of the game move, White should have attached here first.]
    (;
    B[dg]
    C[If Black stands up here, ...];
    W[dl]
    C[... White can play the following sequence in sente.];
    B[el];W[dk];B[dj];W[am];B[ej];W[eh];B[cj];W[de]
    C[After White hanes here, Black's group will have a hard time living.]
    )
        (;
        B[fh]
        C[According to Kato, in order to avoid the previous variation, Black would have to peep here, and then ...];
        W[fi];B[dl]
        C[... the following sequence would occur.];
        W[dg];B[df];W[bg];B[eg];W[cf];B[de];W[gh];B[gg];W[eh];B[fg];W[am];B[dr];W[im]
        TR[cf][bg][dg][ch]
        C[Now with the strong marked ponnuki, White can invade the moyo more deeply to here.

Comparing this result to the game, White is clearly better than the game.]
        )
    )
)

