(;
AB[mp][np][op][pp][qp][rp][sp][jq][kq][lq][mr][qr][rr][sr][os]
AW[mq][nq][oq][pq][qq][rq][sq][lr][nr][pr]
C[Black plays.]
(;
B[ps]
C[Careless move order mistake.];
W[ns]
C[After White blocks here, Black cannot force a liberty shortage.];
B[kr]
C[For example ...];
W[ms];B[ks];W[rs]
)
    (;
    B[ns]
    C[Correct.]
    (;
    W[ms];B[ps]
    C[Now Black can come back here to create a liberty shortage.];
    W[kr];B[jr];W[ks]
    C[Black has a sente seki.]
    )
        (;
        W[ps]
        C[Questionable.];
        B[ls]
        C[This ko is heavier for White.]
        )
    )
)

