@bookwar
Strong agree that math is about creating / evaluating / etc formalisms, not just using them.
There is an important distinction here. When I say principles of design, I mean psychoperceptual things (proportion, hierarchy, ergonomics, etc) and process things (user testing, prototyping, iterative development, etc), none of which (except maybe prototyping, maybe, debatably) are typical of mathematics. And in particular…