Good Empty Triangle / Solution

Empty triangle  

Black wins the semeai. In a real game, even a strong fighter might miss .

Bob Myers: A wonderful tesuji, but not an empty triangle as the term is commonly used, so in that sense this problem is in the wrong place.

Looks like tesuji  

looks good, but is skilful play, and the best Black can do is to make a ko.

Bamboo joint instead?  

Hans: What about black 1?

ChaoSpectre: What about it? I know this is presumptuous for a DDK to say, but doesn't making the bamboo joint here encourage a seki here? Or something else? Playing here is a very nice move, indeed, but doesn't it give sente to white? I can't exactly play this position out from here, so I may be missing out on some huge detail. Would somebody (Possibly Hans?) play this out after ?

Mef: As far as I can tell, white will at least be able to get a ko with through .

Key point  

Bill: is still the key point. White cannot connect.

Likewise, in the previous diagram, should be at .

Ko (2)  

takes ko.

Bill: Does make ko?