(;
AB[oo][op][ro][so][qp][mq][mr][ms][nq][os]
AW[oq][or][pq][pr][rq][nr][ns]
C[Black plays.]
(;
B[sr]
C[This placement on the 2-1 point often works, ...];
W[sq];B[qq];W[qr];B[rr];W[rs]
C[... but White has too many liberties.]
)
    (;
    B[rr]
    C[Another possibility, ...];
    W[sq]
    C[... but White can again descend safely here.];
    B[qq];W[qr]
    )
    (;
    B[sq]
    C[The only move.];
    W[sr];B[rr]
    (;
    W[sp];B[qq];W[qr]
    C[White seems to be alive here, but ...];
    B[rs];W[qs];B[rp];W[ss];B[rr]
    C[Black's throw-in exposes White's liberty problem.];
    W[rs]
    C[Black has a ko to kill the corner.]
    )
        (;
        W[rs]
        C[Also ko.]
        )
    )
)

