(;
AB[nd][pd][qe][rf][qh][cj][ek][bn][cn][dn][jn][do][ho][hp][hq][qo][qp][cp][cq][cr][gp][eq][er][fq][mq][nq][pq][gr]
AW[dd][of][qf][qg][pi][qi][bm][cm][dm][em][en][eo][ep][pn][po][qn][bo][go][dp][dq][dr][ds][fp][lp][mp][np][fr]
TR[bo]
C[Black's response to the marked play?

Source:
    American Go Journal, v35 #4, pp. 32-33
    Jie Li 7d (Black) v. Lin Xuefen 1P
    Commentary:  Jie Li 7d]
(;
B[an]
C[Black should have simply descended here.];
W[cs];B[br];W[bp]
C[And now what should Black do?];
B[ap]
C[The tesuji to live.];
W[bs];B[ar]
C[Black has a seki.  And looking at the whole board, Black has a big lead.]
)
    (;
    B[ao]
    C[In the game, Black makes this very serious mistake.];
    W[cs]
    (;
    B[br]
    C[If Black tries to live, ...];
    W[ap];B[an];W[bp];B[aq];W[bs]
    C[... White kills the corner.]
    )
        (;
        B[bs]
        C[So in the game, Black has no choice but to block here.];
        W[br];B[ar]
        C[A ko is the best that Black has.];
        W[as]
        C[Now what should Black do?];
        B[pl]
        C[Finding a ko threat is hard, so Black invades White's territory.];
        W[bp]
        C[White kills the big corner for about a 25 point gain, but ...];
        B[rl]
        C[... incredibly, by decimating White's moyo and right side, Black now has about an even game!  Black went on to win by 3.5 points.]
        )
    )
)

