(;
AB[qn][rn][qo][qp][pq][nr][pr]
AW[ro][rp][qq][sq][qr]
C[Black plays.]
(;
B[rs]
C[Correct, but an easy move to overlook!]
(;
W[rr];B[qs];W[so];B[sr]
C[Ko.  The best sequence for both sides.]
)
    (;
    W[qs]
    C[A mistake.  White cannot cut off Black's placement.];
    B[rr]
    LB[so:A][rq:B]
    C[A and B are miai for Black to kill.]
    )
)
    (;
    B[rr]
    C[Looks like the vital point, but ...];
    W[rs];B[sr];W[so]
    C[... White makes a 2nd eye.]
    )
)

