"Psst, c'mere," said the shifty-eyed man wearing a long black trenchcoat, as he beckoned me off the rainy street into a damp dark alley. I followed.


"What are you selling?" I asked.


"Geometrical algebra drugs."


"Huh!?"


"Geometry drugs. Ya got your uppers, your downers, your sidewaysers, your inside-outers..."


"Stop right there," I interrupted. "I've never heard of inside-outers."


"Oh, man, you'll love 'em. Makes you feel like M.C. ever-lovin' Escher on a particularly weird day."


"Go on..."


"OK, your inside-outers, your arbitrary bilinear mappers, and here, heh, here are the best ones," he said, pulling out a large clear bottle of orange pills.


"What are those, then?" I asked.


"Givens transformers. They'll rotate you about more planes than you even knew existed."


"Sounds gross. What about those bilinear mappers?"


"There's a whole variety of them. Here's one you'll love -- they call it 'One Over Z' on the street. Take one of these little bad boys and you'll be on speaking terms with the Point at Infinity."