It's brilliant. I'd never seen anything like it before, and I'm wowed:
I got off the metro yesterday and proceeded along with the herd toward the stairs to exit the station. And there it was. One stunning slope of groovin' girl in black silhouette on fuchsia, highlighted with white, promoting iPod.
On approach, the angle of one's glance works with the angle of the stairs to produce one whopping masterstroke of advertising. The image breaks apart as you walk over it.
Maybe that's a metaphor for something.