(;
AB[rm][nn][pn][qn][oo][qo][np][nq][rp][oq][mr][pr][ps][rs]
AW[po][pp][pq][op][qp][qq][qr][rq][rr][or]
C[Black plays.]
(;
B[sq]
C[Fails.];
W[sr];B[os];W[ro]
C[White lives.]
)
    (;
    B[os]
    C[Fails.];
    W[qs];B[sq]
    C[And if Black persists, ...];
    W[ns];B[sr];W[ro];B[so]
    C[... White lives in double ko.]
    )
    (;
    B[sr]
    C[Better, but ...];
    W[sq];B[sp]
    C[... Black has to fight a ko for the corner.]
    )
    (;
    B[sp]
    C[The only killing move.  Now Black can give an eye-stealing atari on either side.]
    (;
    W[ro];B[sr]
    C[A symmetrical position.];
    W[os];B[sq];W[qs];B[rn]
    C[White has only one eye.]
    )
        (;
        W[qs]
        C[No better.];
        B[sr];W[ss];B[sq]
        )
    )
)

