their choices shape the direction and outcome of the games. Role-playing games are a form of interactive and collaborative storytelling. Like novels or films, role-playing games appeal because they engage the imagination. Interactivity is the crucial difference between role-playing games and traditional fiction. Whereas a viewer of a television show is a passive observer, a player at a role-playing game makes choices that affect the story. Such role-playing games extend an older tradition of storytelling games where a small party of friends collaborates to create a story. While simple forms of role-playing exist in traditional children's games such as "cops and robbers", "cowboys and Indians" and "playing house", role-playing games add a level of sophistication and persistence to this basic idea. Participants in a role-playing game will generate specific characters and an ongoing plot. A consistent system of rules and a more or less realistic campaign setting in games aids suspension of disbelief. The level of realism in games ranges from just enough internal consistency to set up a believable story or credible challenge to full-blown simulations of real-world processes.