GNS theory is an informal field of study developed by Ron Edwards which attempts to create a unified theory of how role-playing games work. Focused on player behavior, in GNS theory participants in role-playing games organize their interactions around three categories of engagement: gamism, narrativism and simulationism.
The theory focuses on player interaction rather than statistics, encompassing game design beyond role-playing games. Analysis centers on how player behavior fits the above parameters of engagement and how these preferences shape the content and direction of a game. GNS theory is used by game designers to dissect the elements which attract players to certain types of games.
GNS theory was inspired by the Threefold Model, which was discussed on the rec.games.frp.advocacy USENET group in summer 1997. The Threefold Model defined drama, simulation and game as three paradigms of role-playing. The name "Threefold Model" was coined in a 1997 post by Mary Kuhner outlining the theory. Kuhner posited the theory's central ideas there, and John H. Kim later codified and expanded the discussion.
In his article "System Does Matter", which was originally posted on the Gaming Outpost website in July 1999, Ron Edwards wrote that all RPG players have one of three mutually-exclusive perspectives. According to Edwards, enjoyable RPGs focus on one perspective and a common error in RPG design is to try to include all three types. His article could be seen as a warning against generic role-playing game systems from large developers. Edwards connected GNS theory to game design, popularizing the theory. On December 2, 2005, Edwards closed the forums on the Forge about GNS theory, saying that they had outlived their usefulness.
A gamist makes decisions to satisfy predefined goals in the face of adversity: to win. Edwards wrote,
I might as well get this over with now: the phrase "Role-playing games are not about winning" is the most widespread example of synecdoche in the hobby. Potential Gamist responses, and I think appropriately, include:
"Eat me,"
(upon winning) "I win," and
"C'mon, let's play without these morons."
These decisions are most common in games pitting characters against successively-tougher challenges and opponents, and may not consider why the characters are facing them in the first place. Gamist RPG design emphasizes parity; all player characters should be equally strong and capable of dealing with adversity.