(;AB[fe]AB[ge]AB[gd]AB[hd]AB[id]AB[jd]AB[ff]AB[fg]AB[eh]AB[ei]AB[ej]AB[fj]AB[gk]AB[gh]AB[hh]AB[ih]AB[ig]AB[ii]AB[jj]AB[jk]AB[kc]AB[kg]AB[lg]AB[mf]AB[nf]AB[ne]AB[nc]AW[fk]AW[gl]AW[gj]AW[hj]AW[ij]AW[gi]AW[fi]AW[fh]AW[ji]AW[ki]AW[mh]AW[mg]AW[lf]AW[le]AW[me]AW[je]AW[ie]AW[he]AW[hf]AW[hg]AW[gg]AW[gf]AW[lj]AW[oh]AB[mc]AB[lc]LB[cc:T]C[Kill all the marked stones unconditionally or tenuki at T if not possible]AW[kf]AW[nd]TR[gg]TR[gf]TR[hf]TR[hg]TR[ie]TR[he]TR[je]TR[kf]TR[lf]TR[le]TR[me]LB[ll:T]AP[goproblems]
(;B[ke];W[jg]
(;B[jh];W[jf];B[kh];W[lh])
(;B[jf];W[jh]
(;B[ld];W[kd]C[Ko! If black plays at A, then white lives with B]LB[md:A]LB[if:B])
(;B[md];W[kd];B[ld];W[if])
(;B[kd];W[lh]C[You failed to kill the marked stones...]TR[kf]TR[lf]TR[le]TR[me])
(;B[if];W[lh]TR[lf]TR[kf]TR[le]TR[me]C[Marked stones survive...]))
(;B[kd];W[jf];B[jh];W[kh])
(;B[if];W[jf];B[jh];W[kh]))
(;B[jf];W[jg]
(;B[if];W[ke]
(;B[jh];W[kh];B[md];W[lh])
(;B[md];W[jh]))
(;B[jh];W[kh]
(;B[ke];W[kd]
(;B[hk];W[ik]
(;B[md];W[lh];B[jg]C[];W[hl];B[ld]C[Nice!RIGHT])
(;B[ld];W[lh];B[jg]C[];W[hl];B[md]C[Nice!RIGHT])
(;B[if];W[lh]TR[kf]TR[lf]TR[le]TR[me]C[The marked stones survive...])
(;B[jg];W[lh]
(;B[md];W[hl];B[ld]C[Nice!RIGHT])
(;B[ld];W[hl];B[md]C[Nice!RIGHT])))
(;B[if];W[lh]TR[kf]TR[lf]TR[le]TR[me]C[The marked stones survive...])
(;B[md];W[lh];B[jg];W[hi])
(;B[ld];W[lh];B[jg];W[hi]))
(;B[jg];W[lh]
(;B[hk];W[ik]
(;B[md];W[hl]
(;B[ke];W[kd];B[ld]C[Nice!RIGHT])
(;B[ld]C[Nice!RIGHT]))
(;B[ld];W[hl];B[md]C[Nice!RIGHT])
(;B[ke];W[kd]
(;B[md])
(;B[ld])))
(;B[ke];W[kd]
(;B[hk];W[ik]
(;B[md])
(;B[ld]))
(;B[md];W[hi])
(;B[ld];W[hi]))
(;B[md];W[hi])
(;B[ld];W[hi]))
(;B[hk];W[ik]
(;B[jg];W[lh]
(;B[md];W[hl]
(;B[ke];W[kd];B[ld]C[Nice!RIGHT])
(;B[ld]C[Nice!RIGHT]))
(;B[ld];W[hl];B[md]C[Nice!RIGHT])
(;B[ke];W[kd]))
(;B[md];W[lh];B[jg];W[hl]
(;B[ke];W[kd];B[ld]C[Nice!RIGHT])
(;B[ld]C[Nice!RIGHT]))
(;B[ke];W[kd]
(;B[md];W[lh];B[jg]C[];W[hl];B[ld]C[Nice!RIGHT])
(;B[ld];W[lh];B[jg]C[];W[hl];B[md]C[Nice!RIGHT])
(;B[if];W[lh]TR[kf]TR[lf]TR[le]TR[me]C[The marked stones survive...])
(;B[jg];W[lh]
(;B[md])
(;B[ld])))
(;B[ld];W[lh];B[jg];W[hl];B[md]C[Nice!RIGHT])
(;B[if];W[ke];B[md];W[lh]))
(;B[md];W[lh];B[jg];W[hi])
(;B[ld];W[lh];B[jg];W[hi]))
(;B[ke];W[jh]
(;B[ld];W[kd]C[Ko! If black plays at A, then white lives with B]LB[md:A]LB[if:B])
(;B[md];W[kd];B[ld];W[if])
(;B[kd];W[lh]C[You failed to kill the marked stones...]TR[kf]TR[lf]TR[le]TR[me])
(;B[if];W[lh]TR[lf]TR[kf]TR[le]TR[me]C[Marked stones survive...])))
(;B[jg];W[od];B[md];W[of]TR[kf]TR[lf]TR[le]TR[me]C[You can't kill the marked stones anymore...])
(;B[md];W[jg]
(;B[jh];W[jf]
(;B[kh];W[lh]
(;B[ld];W[hi])
(;B[hk];W[if]))
(;B[ld];W[kh]))
(;B[jf];W[kh];B[jh];W[lh];B[jg];W[hi])))