(;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]))