(;
AB[pn][rn][qo][mp][np][op][pp][kq][lq][qq][rq][rr]
AW[qp][rp][nq][oq][pq][mr][qr][qs]
C[Black plays.]
(;
B[rs]
C[A forcing move, but a big mistake.];
W[os]
C[White takes a vital point to live.]
)
    (;
    B[lr]
    C[Also a big mistake.];
    W[rs]
    C[White can force here 1st, and then ...];
    B[sp];W[ms]
    C[... complete a standard living shape.  Note that White is alive, even without the marked liberty.]
    TR[mq]
    )
    (;
    B[os]
    C[Black's placement here is the right idea, but the wrong point.];
    W[rs];B[sp];W[ns];B[or];W[lr];B[kr];W[ls];B[nr]
    )
    (;
    B[or]
    C[The correct point.]
    (;
    W[os];B[ns];W[pr]
    C[White has to fight a ko to live.]
    )
        (;
        W[lr];B[kr];W[os];B[ns];W[pr]
        C[Still a ko.]
        )
    )
)

