One of the principal pleasures offered by both video games and social media is the experience of flow. Flow is an aesthetic principle for first-person shooter games, for platform games, for puzzle games. It is also the state induced by watching one YouTube video or Netflix episode after another or by monitoring Facebook feeds for hours on end. As early as the 1970s, the psychologist Mihaly Csikszentmihalyi (1991) applied the term "flow" to describe a particular state that he had identified in his subjects: "I developed a theory of optimal experience based on the concept of flow, a state in which people are so involved in an activity that nothing else seems to matter; the experience itself is so enjoyable that people will do it even at great cost, for the sheer sake of doing it."