“ As Prof. Wagner points out, Apple is great at protecting their innovations. Look at the click wheel—it’s without a doubt the most elegant way to navigate an MP3 player’s interface, and no one has been able to mimic it exactly. Others have clickable buttons, and touch-sensitive controllers, some of which are shaped like wheels, but Apple has been able to protect the specifics of the clickwheel—all of these elements combined—that make it special.”
Source: Gizmodo
