KarlKnechtel: This looks to me a lot harder than exercise 162 or 163, so I thought I'd give it a shot. I'm pretty sure this is correct:
looks odd, but seems to be an example of guzumi. White cannot yet atari Black's empty triangle on either side, due to damezumari - White must play at a first before b. And since
would take the vital point of a bulky five, White has no time for this capturing plan - she must play
herself, answering the empty triangle with one of her own.
That's the key; Black has now secured the bottom eye in sente (by threatening to make a second eye there), giving him time to complete the second eye at the top. makes miai of the c's and of the d's.
Later, White forces with Wa, Be, Wb, Bf. There is still lots of aji here! Note that Ba doesn't really help Black any, though it does give him one ko threat versus the several that White can get out of the position. is better than playing it at 3, even though it fails; the points available to Black are the same, and White gets more threats. I don't think I'm qualified to compare
vs. tenuki, though.