HTC Incredible S auto-rotating buttons explained? (video)

We were quite bedazzled by the HTC Incredible S after our hands-on at MWC, but it's the auto-rotating icons for the capacitive buttons that left us most intrigued. So we went back to the HTC booth to try to make sense of it all. From what we were able to observe, there's some optical trickery happening here: the icons
appear to be glittering and shimmering depending on viewing angle as if lit through a prism, half-mirror or grate of some kind. We think that a pair of LEDs are used to project the intended icon onto the glass surface via either a combination of prisms and half-mirrors, or via horizontally and vertically polarized grates. Watch our video after the break, and let us know in the comments how you think this actually works.