(;GM[1]FF[4]CA[UTF-8]
SZ[19]RU[Japanese]KM[0]TM[1800,0,30,5]PW[]PB[]AB[qd]AW[dp]AB[pp]AW[dd]AB[fc]AW[ee]AB[db]AW[gd]AB[gc]AW[hd]AB[ic][cc]AW[cd][cn]AB[id]AW[ie]AB[je]AW[jf]AB[ke][if]AW[he][ig]AB[bf]AW[be]AB[cj]AW[bh]AB[ch]AW[bg]PL[B]TR[bg]C[black invaded, white just played the marked stone. how to respond?]
(;B[bi]CR[bi]
;W[cl]CR[cl]C[was your move really sente? if not, white got a key point...]
(;B[cf]CR[cf]
;W[cg]CR[cg]
(;B[dg]CR[dg]
;W[dh]CR[dh]
(;B[ah]CR[ah]
;W[ci]CR[ci]
;B[ag]CR[ag]
;W[ch]CR[ch]
;B[eh]CR[eh]C[RIGHT
black catches white in a ladder])
(;B[ag]CR[ag]
;W[ci]CR[ci]
;B[ah]CR[ah]
;W[ch]CR[ch]
;B[eh]CR[eh]C[RIGHT
black catches white in a ladder])
(;B[di]CR[di]C[ko is no go]))
(;B[ah]CR[ah]
;W[dg]CR[dg])
(;B[dh]CR[dh]
;W[dg]CR[dg]C[bad for black]))
(;B[cg]CR[cg]
;W[cf]CR[cf]
;B[af]CR[af]
;W[ae]CR[ae]C[easy for white]))
(;B[cg]CR[cg]
;W[bi]CR[bi]
(;B[cf]CR[cf]
;W[af]CR[af])
(;B[af]CR[af]
;W[cf]CR[cf])
(;B[bj]CR[bj]
;W[ci]CR[ci]
;B[di]CR[di]
;W[dj]CR[dj]
;B[af]CR[af]
;W[cf]CR[cf]))
(;B[cf]CR[cf]
;W[bi]CR[bi]C[easy for white to escape])
(;B[bl]CR[bl]C[wrong direction])
(;B[cm]CR[cm]C[wrong direction])
(;B[dl]CR[dl]C[wrong direction])
(;B[bm]CR[bm]C[wrong direction])
(;B[cl]CR[cl]C[wrong direction])
(;B[ei]CR[ei]C[wrong direction]))