Thank you to Morten's problem 379 for the pre-game practice.
(;AP[goproblems]AB[ja]AB[jc]AB[ib]AB[jb]AB[kb]AB[lc]AB[mc]AB[nc]AB[nb]AB[ob]AW[pb]AW[pc]AW[oc]AW[nd]AW[md]AW[ld]AW[kc]AW[kd]AW[jd]AW[ic]AW[hc]AW[hb]TR[jb]C[Black just played the marked stone. Can white punish that mistake?](;W[la];B[ma](;W[lb];B[oa]C[CHOICE](;W[pa]C[Well done! Black cannot approach from either side.RIGHT])(;W[ha];B[mb])(;W[mb];B[ka])(;W[ka];B[mb]))(;W[oa];B[lb])(;W[ha];B[lb])(;W[ka];B[lb]))(;W[ma];B[la](;W[oa];B[na])(;W[na];B[oa])(;W[mb];B[sa]C[Black plays elsewhere.];W[oa];B[lb]))(;W[oa];B[la](;W[ma])(;W[na];B[ma])(;W[mb];B[sa]C[Black plays elsewhere.](;W[na];B[lb])(;W[ma])))(;W[lb];B[la](;W[ma];B[mb])(;W[oa];B[na])(;W[na];B[oa]))(;W[pa];B[la](;W[oa];B[na])(;W[na];B[oa])(;W[ma];B[oa]))(;W[na];B[la](;W[oa])(;W[ma])(;W[mb];B[ma]))(;W[mb];B[la](;W[oa])(;W[na])(;W[ma]))(;W[ha];B[la]))