“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 of Infinity.”