The HTC Incredible S is the first smartphone with rotating button inscriptions. Sure, it’s not a big deal, but our geeky minds just wouldn’t let us sleep until we found how they did it.
Well luckily our insomnia was short-lived as we managed to get to the bottom of this quite easily. To make a long story short: the back-lit icons of the capacitive touch buttons on the Incredible S are composed of tiny LEDs.
You’ve got a group of tiny LEDs that compose the icons in one direction and another group of LEDs that compose its rotated version. Of course there is some intersection, which means that some LEDs are always lit, but that’s of little importance.
This theory is confirmed by the following close up picture – you can see the turned-off LEDs that compose the inverted arrow. I’ve added the red outline to help you discern it a bit easier. There’s no LEDs for a third arrow so you that’s why this trick only works when you rotate the Incredible S to the left.
It also explains the not perfectly even distribution of the pixels – the acceptable error margin with this technology, which involves physically putting and aligning the LEDs.