Flow (stylized as flOw) is an indie video game created by Jenova Chen and Nicholas Clark. Originally released as a free Flash game in 2006 to accompany Chen's master's thesis, it was reworked into a 2007 PlayStation 3 game by his development studio, thatgamecompany. SuperVillain Studios released a PlayStation Portable version of the game in 2008, and PlayStation 4 and PlayStation Vita versions in 2013. In Flow, the player navigates a series of two-dimensional (2D) planes with an aquatic microorganism that evolves by consuming other microorganisms. The game's design is based on Chen's research into dynamic difficulty adjustment at the University of Southern California's Interactive Media Division, and on psychologist Mihaly Csikszentmihalyi's theoretical concept of mental immersion or flow.