Mercedes wanted to make a dramatic statement about how its new B-Class F-Cell car passes through the environment without leaving a trace, so it placed it behind an invisible LED curtain. We wanted to (not?) see that for ourselves at the Paris Auto Show, so took a quick tour of the magic LED cloak and the technology behind it. It doesn't work quite as well in a show hall as it did when we first saw it in its natural habitat, but the system was still a fun way to show off Merc's green ambitions. It works by passing video from behind the car taken with a Sony video camera through a laptop to a 200 x 300 resolution LED curtain. That makes the car blend in with its background, which is what such a car would do in the real world as far as its emissions go -- apart from a little water, of course. See the video below for the complete technical explanation.