The thriller is an all-encompassing umbrella genre that corrals all other genres underneath it. It is difficult to determine if a movie is only a thriller. The most popular sub-genres of the thriller include spy, detective, psychological, horror, action, and supernatural thrillers. Thrillers habitually mix the tenants of other genres in a single film as well as the tenants of the sub-genres of the thriller. The main ingredient of a thriller is suspense, excitement, and tension, whereby thrillers set out to evoke an emotional reaction. Thrillers often create an atmosphere of creeping menace and sudden outbursts of violence, crime, and murder. Gunfights and chase scene are common set pieces. One of the main themes of thrillers is the existence of a double world – one civilized and one savage. In Hollywood, the dark corrupt, dangerous, savage world is usually overcome by the status quo, but with lingering side effects. Thrillers also favor, loose, episodic structures with labyrinthine, maze-like plots, filled with myriad twists and tangles. There is a loss of control for both hero and spectator. Both hero and spectator become tangled up and a part of the same mysterious world that they are investigating.