[jhy]

And it was only parallax pseudo-3D. It wasn't anything like the 3DS lenticular stereo effect. Four (!) head-tracking cameras on the front tried to understand where you were looking, and then the UI would shift about in response. There was no convincing 3D effect.

The intention was that the UI would reveal extra info (like meta-data about a photo, or calendar details) when you shifted your head POV. Like a gesture that you could do one-handed while riding the bus. (But not discoverable, and twitchy, and tail-wagging-the-dog.)

Given how coarse the tracking had to be so that the UI wasn't constantly shifting, it would have been far simpler and more energy efficient just to use the accelerometer instead of the fancy camera setup. And just use that for some nice parallax effects in the launcher; not as a core UI interaction.