“Because this state is so desirable, both for productivity and for pleasure, many application (web and mobile) designers are starting to try to design for it as well. This is a daunting task. First, all humans are different. This means in identical situations I hit flow at a very different moment in the ease-to-difficulty continuum than you do. Secondly, flow is extremely easily to disrupt.”

(Christina Wodtke a.k.a. @cwodtke ~ Boxes and Arrows)