He gives a little context on page 6: "Worse, there are often no perceived affordances for how various screen elements respond when touched. The prevailing aesth

He gives a little context on page 6: "Worse, there are often no perceived affordances for how various screen elements respond when touched. The prevailing aesthetic is very much that of flat images that fill the screen as if they were etched. There’s no lighting model or pseudo-dimensionality to indicate raised or lowered visual elements that call out to be activated."