(;AB[sb]AB[rc]AB[qc]AB[pc]AW[nc]AW[oe]AW[qd]AW[rd]AW[sc]AW[re]AW[qf]AW[pe]AB[pd]AW[nb]AW[nd]AW[oc]AB[ob]AB[pa]AW[na]AP[goproblems]
(;B[ra]TR[sa]TR[rb]C[Creates an eye in the corner which is a useful shape in many positions.RIGHT])
(;B[rb];W[ra];B[qa];W[pb]
(;B[oa];W[qb])
(;B[qb];W[oa])
(;B[sa];W[oa]))
(;B[oa];W[ra]
(;B[qa];W[qb]
(;B[pb];W[rb])
(;B[rb];W[pb]))
(;B[qb];W[qa])
(;B[rb];W[qa]))
(;B[pb];W[ra]C[Bulky five]MA[qa]MA[qb]MA[rb]MA[sa])
(;B[qb];W[ra]C[Black is dead because white could fill the outside liberties. Then black is left with a killable or dead shape inside.]
(;B[oa];W[qa])
(;B[qa];W[oa]TR[rb]C[Black only has one eye.]))
(;B[sa]LB[pf:T]
(;W[oa]
(;B[pb]MA[qa]MA[ra]MA[rb]MA[qb]C[White can almost fill the marked points.])
(;B[qb];W[ra])
(;B[qa];W[pb])
(;B[rb]MA[pb]MA[qa]C[Black needs both the marked points to live.])
(;B[ra]MA[pb]MA[qb]C[Black needs both of the marked points to live.]))
(;W[pf]C[White tenukis]))
(;B[sd];W[ra];B[qa]LB[pf:T];W[pf]C[White tenukis; black needs both P19 and S18 to live.]
(;B[oa];W[qb];B[pb];W[rb]C[White almost fills with a tripod dead shape. White cuts off escape and as long as the white groups live black is dead.]TR[qb]TR[rb]TR[ra])
(;B[rb];W[pb]))
(;B[qa];W[rb]
(;B[ra];W[sa];B[qb];W[sb];B[sd];W[sb]
(;B[oa];W[sc])
(;B[sc];W[oa]))
(;B[qb];W[sa];B[ra];W[sb];B[sd];W[sb]MA[oa]MA[sc]C[P19 and T17 are miai.]
(;B[oa];W[sc])
(;B[sc];W[oa]))))