(;AB[cs]AB[fs]AB[er]AB[dr]AB[cq]AB[bq]AW[ap]AW[bp]AW[cp]AW[dq]AW[eq]AW[fq]AW[fr]AW[hr]AW[bs]C[4. Black to live]AP[goproblems] (;B[ar];W[br];B[es];W[aq];B[cr]LB[ar:1]LB[br:2]LB[es:3]LB[aq:4]C[Black 1 threatens 2, and if White plays there, Black plays 3. White 4 and Black 5 then create another snapback. RIGHT]) (;B[br];W[ar];B[as];W[aq];B[es]LB[br:1]LB[ar:2]LB[as:3]LB[aq:4]LB[es:5]C[Black 1 here is a bit too obvious. White 2 is the key point, and the result is a ko. CHOICE]) (;B[es];W[ar] (;B[br];W[aq];B[as]C[ko]) (;B[aq];W[cr])))