>Playing With Pyramids says in multiple places that a koan has one or >more pyramids. Ah. Well, I didn't learn Zendo from Playing With Pyramids. I learned it from Kory Heath. :-) But that was almost 10 years ago; the rules may have changed since then. >The null koan is an obvious variant that lots of >people allow, but I prefer to disallow it because of the ambiguity of >rules like "contains only grounded pyramids". Ambiguity is not unique to the null koan. Consider "AKHTBN if all of its blue pyramids are upright". A koan without any blue pieces is just as ambiguous.