I’ve come to think of software applications as a form of digital architecture: some are places of concentration, others of collaboration, others clearly just for fun. Software’s emotional dimension is crucial: how it feels dictates how it’s used. (Architects hire environmental psychologists; tech companies hire user-experience researchers.) Microsoft Word is the quiet room at the university library; personal Gmail is a dirty kitchen, yesterday’s plates stacked next to the sink; Twitter is an overcrowded bar. Throughout the day, I’ll move from room to room, alternating between solitude and socializing, work and play.