(;
AB[mo][no][oo][ro][jp][jq][jr][js][kp][lp][op][pp][qp][rq][rr][qs]
AW[mp][np][lq][pq][pr][qq][kr][mr][nr]
C[Black plays.]
(;
B[ps]
C[Pushing in here looks obvious, but doesn't work.];
W[os]
C[Blocking gives White just enough space to live.]
(;
B[ls];W[oq];B[mq];W[nq]
LB[lr:A][ms:B]
C[A and B are miai for White to live.]
)
    (;
    B[nq];W[mq];B[oq];W[ls]
    C[Again, White lives.]
    )
)
    (;
    B[nq]
    C[Correct.];
    W[mq]
    (;
    B[oq]
    C[Fails.];
    W[ls]
    C[White lives.]
    )
        (;
        B[ns]
        C[A good follow-up!]
        (;
        W[oq];B[ps];W[os]
        C[White has to fight a ko, which is the best result for both sides.]
        )
            (;
            W[ls]
            C[A mistake.  Now White cannot even make a ko.];
            B[ps];W[oq];B[os];W[or];B[ms]
            C[White cannot make another eye.]
            )
        )
    )
)

