you know, testing on dogs has indicated that they're not supposed to be able to figure something like this out - they're notoriously bad at "problem solving". and i'm not convinced this is luck, either - it seems to get the geometry.

my understanding is that wild predators - lions, especially, but also wolves - need to have an intuitive concept of geometry in order to carry out the hunts they carry out, which often have to do with using angles to their advantage. it's a base, intuitive understanding of trigonometry. and it's both taught behaviour and necessary for survival.

but, this is unexpected in a domestic dog.