(;AB[qq]AB[pq]AW[oq]AW[nq]AW[pp]AW[qp]AW[qm]C[Black to play and make a ko]AB[lm]AP[goproblems] (;B[rp];W[ro];B[rr];W[sp];B[sq] (;W[rq]LB[rp:1]LB[ro:2]LB[rr:3]LB[sp:4]LB[sq:5]LB[rq:6]C[In this shape, playing a hane at 1 and answering White's block at 2 with the open connection of Black 3 is the only possibility. In response to White's atari at 4, Black blocks at 5 and White 6 starts a ko fight.RIGHT]) (;W[so];B[or];W[nr];B[pr];W[rq];B[sr]LB[so:1]LB[or:2]LB[nr:3]LB[pr:4]LB[rq:5]LB[sr:6]C[In the previous diagram, White has no choice but to fight the ko, but let's suppose he connects at 1. What happens? Black can simply hane and connect at 2 and 4. When White captures at 5, Black connects at 6 and has a living shape. Consequently, unless White is totally unable to fight the ko, White 1 is strange.RIGHT])) (;B[rr];W[rp];B[or];W[nr] (;B[qs];W[pr];B[os];W[rq]LB[rr:1]LB[rp:2]LB[or:3]LB[nr:4]LB[qs:5]LB[pr:6]LB[os:7]LB[rq:8]C[Lets take a look at Black 1, the move which allowed him to live in the previous pattern. After White 2, Black tries the technique of Black 3 to 5. This time, however, White cuts at 6 and puts the two black stones in atari. Next, after Black 'a' and White 'b', Black is dead.CHOICE]) (;B[ps]LB[sr:a]LB[qr:b]LB[rr:1]LB[rp:2]LB[or:3]LB[nr:4]LB[ps:5]C[After Black 1 and White 2, what about the hand and open connection of Black 3 and 5? If White continues at 'a' and Black connects at 'b', making a ko, then this would also be a possible solution. That is not, however, the way things will proceed. White has the clever attack shown in the next diagram.];W[ns]LB[rr:1]LB[rp:2]LB[or:3]LB[nr:4]LB[ps:5]C[After Black 1 and White 2, what about the hand and open connection of Black 3 and 5? If White continues at 'a' and Black connects at 'b', making a ko, then this would also be a possible solution. That is not, however, the way things will proceed. White has the clever attack shown in the next diagram.]LB[sr:a]LB[qr:b];B[qs];W[rq];B[sr];W[pr]LB[sq:a]LB[rs:b]LB[ns:1]LB[qs:2]LB[rq:3]LB[sr:4]LB[pr:5]C[After the previous diagram, White's descent at 1 is a deadly move. After Black fills his gap at 2, White plays 3 and, in response to Black's descent to 4, throws in at 5, turning the left side into a false eye. If instead of 2, Black plays 3, you shouldverify for yourself that after White 'a', Black 4, and the attachment at White 'b', Black is dead.])) (;B[or];W[nr] (;B[ps];W[rq];B[rr];W[qr];B[pr];W[sr]LB[or:1]LB[nr:2]LB[ps:3]LB[rq:4]LB[rr:5]LB[qr:6]LB[pr:7]LB[sr:8]C[What about beginning with the hane and open connection of Black 1 and 3? This, however, is not a very resilient shape. White s hane at 4, cut at 6, and atari at 8 kill Black easily.CHOICE]) (;B[qr]LB[or:1]LB[nr:2]LB[qr:3]C[After Black 1 and White 2, take a look at Black's turn at 3. This is quite a tenacious shape. How should White attack this group? If White had a stone at 'a', then without bothering to make a ko, he would simply capture the black group unconditionally. Lets deal with this in our next problem.CHOICE]LB[lr:a])))