Flow

In Flow, the player guides a small, multi-segmented worm or snake-like creature through an aquatic environment. There are no menus or guidelines; the game begins immediately. The game world, which is viewed from a top-down perspective, consists of two-dimensional planes stacked vertically upon each other. A blurred version of the layer below appears in the background of each plane.

Planes contain organisms of varying sizes; the player's creature automatically attempts to consume them when they are nearby. The majority of these creatures are non-confrontational and are composed of cells that increase the number of segments in the player's creature when eaten. All planes, except for the highest and lowest, contain two specially colored organisms that move the player's creature up or down one plane when touched.

Flow was originally developed as part of Jenova Chen's master's thesis for the Interactive Media Program at the University of Southern California's School of Cinematic Arts. His thesis was on the concept of dynamic difficulty adjustment (DDA), wherein a game adjusts its reactions to a player based on the past and present actions of that player. He illustrated his ideas with Flow, which he created in collaboration with Nicholas Clark. Chen implemented DDA by causing the player to change the game's difficulty subconsciously; he allowed players to dive between planes at will and provided the option of eating or not eating any creature.

Players may decide to rush downwards or to grow stronger before attacking powerful opponents. Chen described Flow as "A simple game. It's the simplest test of active DDA." Another influence on the game was psychologist Mihaly Csikszentmihalyi's work on flow, wherein a person fully immerses themselves in an activity and gains a feeling of energized focus.

The Flash version of Flow received 100,000 downloads within its first two weeks of release. 5 million times. Its PlayStation 3 re-release was the most downloaded game on the PlayStation Network in 2007. Flow received the 2008 Game Developers Choice Awards nominations for the Innovation Award and Best Debut, and was presented with Best Downloadable Game.

Flow was nominated for Downloadable Game of the Year at the AIAS' 11th Annual Interactive Achievement Awards, and for the Best Innovation award at the British Academy of Film and Television Arts's 4th British Academy Games Awards. Its music garnered nominations for Best Interactive Score and Most Innovative Use of Audio from the Game Audio Network Guild, and won composer Austin Wintory the Rookie of the Year award. Flow was a finalist at the 2007 Slamdance Guerrilla Games Competition, but withdrew along with several other finalists after Super Columbine Massacre RPG! was removed from the competition.