(;AW[qb]AW[pb]AW[pc]AW[od]AW[nd]AW[md]AW[ld]AW[kd]AW[ne]AW[jd]AW[hc]AB[qa]AB[rb]AB[rc]AB[qc]AB[pd]AB[qe]AB[oe]AB[of]AB[nf]AB[mf]AB[me]AB[ke]C[At some point in the game it will be worthwhile to play here. Especially if you can make your opponent play the last move.]AP[goproblems] (;B[oa] (;W[nb]C[(White's best defense)] (;B[pa];W[na]C[4 points gained in sente; the best result. Black can gain another point by playing at P18; but that would be gote, so it will have to wait until the end of the game.RIGHT]MA[ob]) (;B[na];W[pa]) (;B[ob];W[oc];B[pa];W[na];B[ra]C[5 points in gote; one point better than the solution, but you lost sente; so one move worse. You should not play like this unless it is the last point on the board.]) (;B[oc];W[ob];B[pa];W[na];B[ra]C[Just 3 points in gote.])) (;W[ob];B[nb]C[White P18 would be bad; after Black O18 White cannot cut, so Black takes a huge chunk out of White's side.RIGHT]) (;W[pa];B[oc];W[ra];B[ob]C[This would of course be a complete disaster to White.RIGHT]) (;W[na];B[nb] (;W[pa];B[oc]C[Another line White should avoid; snapback.RIGHT]) (;W[ob];B[ma]C[White can't cut and loses the side territory.RIGHT])) (;W[nc];B[nb] (;W[pa];B[oc]C[Snapback...RIGHT]) (;W[mb];B[pa];W[oc];B[ma];W[la];B[na];W[lb]C[A huge reduction (and still sente!)RIGHT])) (;W[oc];B[pa];W[nb];B[na];W[lb];B[la];W[ka];B[ma];W[kb]C[Black would be delighted with this sente reduction...RIGHT])) (;B[pa];W[oa] (;B[ra];W[ob]C[Just 2 points in sente.]) (;B[oc];W[ob] (;B[ra]C[One point in gote. Sure you can do better than this.]) (;B[nb];W[ra] (;B[qa];W[nc]C[This will not gain Black anything.]) (;B[nc];W[qa]C[Black loses the semeai and any chance at profit in the corner.])) (;B[nc];W[ra] (;B[nb];W[qa]C[Black loses the semeai and any chance at profit in the corner.]) (;B[qa];W[nb]C[Black gains nothing.]) (;B[mc];W[qa]C[Black will lose the semeai.]) (;B[mb];W[mc];B[nb];W[lb]C[No chance.]))) (;B[ob];W[ra])) (;B[na];W[pa];B[oc];W[ob]) (;B[ob];W[oc];B[pa];W[nb] (;B[oa];W[na];B[ra]C[5 points in gote; one point better than the solution, but you lost sente; so one move worse. You should not play like this unless it is the last point on the board.]) (;B[ra];W[oa]C[Just 2 points in sente. Also White could postpone P2 taking sente at the cost of just a few points extra.]) (;B[na];W[ma]MA[na]MA[ob]C[Ouch. You lost 2 stones. In total you just gained 2 points in sente.])) (;B[oc];W[ob] (;B[pa];W[oa] (;B[ra]C[One point in gote. Sure you can do better than this.]) (;B[nb];W[ra] (;B[qa];W[nc]C[This will not gain Black anything.]) (;B[nc];W[qa]C[Black loses the semeai and any chance at profit in the corner.])) (;B[nc];W[ra] (;B[nb]) (;B[qa];W[nb]C[Black gains nothing.]) (;B[mc];W[qa]C[Black will lose the semeai.]) (;B[mb];W[mc];B[nb];W[lb]C[No chance.]))) (;B[oa];W[nb];B[pa];W[na];B[ra]C[Just 3 points in gote.]) (;B[nb];W[nc] (;B[oa];W[mb] (;B[ma];W[la] (;B[pa];W[na];B[ra]C[When the smoke clears all Black has gained was 3 points in gote.]) (;B[ra]C[White can tenuki now; Black has just 3 points in gote.]) (;B[na];W[pa])) (;B[pa];W[na]) (;B[na];W[ma]) (;B[ra];W[na]C[About 2 points in sente (3 in gote or 1 if White gets to play O19).])) (;B[pa];W[oa]) (;B[na];W[pa])) (;B[nc];W[nb])) (;B[nb];W[oc]) (;B[ra];W[pa]C[0 points in sente]))