(;AB[pj][jp][mp][pp]LB[qq:A][qp:B][ro:C][ql:D] C[White can invade at any of the labelled points, but only 'A' is considered here. ---- Please play at 'A' to start. FORCE] ;W[qq];B[qp] (;W[rp];B[ro];W[rr];B[sp];W[sq]C[You got a ko, but unconditional life in sente is possible.]) (;W[rq]C[NOTTHIS]) (;W[pq];B[nq] (;W[nr]C[NOTTHIS]) (;W[op]C[NOTTHIS]) (;W[oq]C[NOTTHIS]) (;W[or]C[NOTTHIS]) (;W[rp];B[ro] (;W[nr]C[NOTTHIS]) (;W[op]C[NOTTHIS]) (;W[oq]C[NOTTHIS]) (;W[or]C[NOTTHIS]) (;W[rr];B[sp];W[sq]C[The ko is not required, as white can live in sente unconditionally.]) (;W[rq];B[qn] C[RIGHT White has made ~5 points, ruined black's corner, caused overconcentration of his forces, and kept sente. The invasion is worth ~25 points.])) (;W[rq];B[rp] (;W[oq];B[op];W[nr];B[mr];W[or]C[You live in gote. The reduction in black's territory is similar to the solution, but loss of sente makes this inferior.]) (;W[nr];B[mr];W[oq];B[op];W[or]C[You live in gote. The reduction in black's territory is similar to the solution, but loss of sente makes this inferior.]))) (;W[pr];B[pq];W[rr];B[or];W[rp];B[ro]LB[qs:A][sq:B]C[You can leave a ko behind, or live playing 'A' or 'B'. The reduction in black's territory is ~6 points smaller than the solution.]))