Psst, cmere, 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. Ive never heard of inside-outers.

Oh, man, youll 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. Theyll rotate you about more planes than you even knew existed.

Sounds gross. What about those bilinear mappers?

Theres a whole variety of them. Heres one youll love — they call it One Over Z on the street. Take one of these little bad boys and youll be on speaking terms with the Point at Infinity.