“Physicists often have to construct clean, clear-cut models to describe messy realities. They do this by cleaning up their concepts about reality, assuming things like frictionless surfaces, lossless mirrors, and yes, spherical objects. UX designers often do the same thing, assuming a spherical user (…) who knows what he wants to do and takes the logical path in achieving his goals. Our scenarios describe happy paths that lead to success for this user.” (Mike Hughes ~ UXmatters)