So I was fiddling around with this today - a Tron Legacy ID disk (yes I'm aware it's not exactly a perfect replica, but the basic idea is there - which is good enough for learning purposes), after the triumph of following along with the Rhino tutorial, I figured I was on a roll...



And was wondering how to get the little inset detailing like you see here:



Basically what's the best approach to adding details like these insets (or whatever the technical term is for them) for example?