(;
AB[op][pp][qp][rp][kq][nq][nr][rq][lr][or]
AW[kp][mp][np][lq][oq][pq][qq][ir][jr][kr][pr][rr][sr][qs]
C[Black plays.]
(;
B[mq]
C[A mistake.  Black loses a crucial liberty with this atari.];
W[lp];B[os]
C[This descent seems to be forcing against the corner, but ...];
W[ms];B[ps];W[qr];B[ls];W[ks]
C[... White wins the semeai by one move.]
)
    (;
    B[rs]
    C[That this move could be helpful seems impossible!]
    (;
    W[mr];B[ps]
    C[But this throw-in exposes White's liberty shortage.];
    W[os];B[ns];W[mq]
    C[Black has a ko to kill the corner.];
    B[ps];W[qr];B[sq]
    C[And White takes 1st.]
    )
        (;
        W[mq]
        C[Transposes.];
        B[ps];W[os];B[ns];W[mr]
        )
    )
)

