(;
AB[or][nr][mq][lq][kq][kp][ip][iq][hq][gq][gp][ep][eq][dr][cr][ho]
AW[mr][lr][kr][jq][ir][hr][gr][fq][er]
C[Black plays.

This problem is harder than appearances, so some readers may want to just play through the variations to practice recognizing living and dead shapes.]
(;
B[es]
C[Too slow.];
W[js]
LB[is:A][ks:B]
C[White takes the vital point to instantly make 2 eyes at A and B.]
)
    (;
    B[js]
    C[Black can take away the vital point, but ...];
    W[jr]
    C[... White solidifies the shape.]
    (;
    B[es];W[ms];B[ks];W[fs]
    LB[gs:A]
    C[At worst, White can now create a seki with A.]
    )
        (;
        B[fs]
        C[No better.];
        W[ms];B[ks];W[is];B[gs];W[es]
        C[White lives with territory.]
        )
    )
    (;
    B[ms]
    C[The only move that works!]
    (;
    W[ls]
    C[The best defense.];
    B[js]
    C[Forced, otherwise White plays here to live instantly.]
    (;
    W[jr]
    (;
    B[es];W[fs]
    C[Black has a ko.  This result is best for both sides.]
    )
        (;
        B[is]
        C[Mistake.];
        W[fs];B[hs]
        C[Black only has a seki.]
        )
        (;
        B[fs]
        C[Even worse.];
        W[es];B[fr];W[gs]
        C[White lives.]
        )
    )
        (;
        W[is]
        C[Mistake.];
        B[jr];W[ks];B[jr]
        C[White dies.]
        )
    )
        (;
        W[es]
        C[Mistake.]
        (;
        B[fr]
        (;
        W[fs];B[ls];W[ks];B[jr];W[js];B[hs]
        C[White dies.]
        )
            (;
            W[ls]
            C[No better.];
            B[js];W[jr]
            C[White seems to be alive, but ...];
            B[fp]
            C[... Black has this nice move.];
            W[is];B[gs]
            C[White dies.]
            )
        )
            (;
            B[ls]
            C[Too slow.];
            W[fr];B[gs];W[jr];B[hs];W[ks];B[is]
            C[Seki.]
            )
        )
        (;
        W[jr]
        C[Mistake.];
        B[ls];W[es];B[fr];W[ks];B[is];W[hs];B[fs];W[gs];B[fr];W[ns];B[ms]
        C[White dies.]
        )
    )
)

