A film genre is a motion-picture category based (for example) on similarities either in the narrative elements or in the emotional response to the film (namely: serious, comic, etc.). Most theories of film genre borrow from literary-genre criticism. Each film genre is associated[by whom?] with "conventions, iconography, settings, narratives, characters and actors". Standard genre characters vary according to the film genre; for film noir, for example, standard characters include the femme fatale and the "hardboiled" detective; a Western film may portray the schoolmarm and the gunfighter. Some actors acquire a reputation linked to a single genre, such as John Wayne (the Western) or Fred Astaire (the musical). A film's genre will influence the use of filmmaking styles and techniques, such as the use of flashbacks and low-key lighting in film noir, tight framing in horror films, fonts that look like rough-hewn logs for the titles of Western films, or the "scrawled" title-font and credits of Se7en (1995), a film about a serial killer. As well, genres have associated film-scoring conventions, such as lush string orchestras for romantic melodramas or electronic music for science-fiction films. The basic genres include fiction and documentary, from which subgenres have emerged, such as docufiction and docudrama. Other examples of subgenres include the courtroom- and trial-focused drama known as the legal drama, which is a subtype of drama. Types of fiction which may seem unrelated can also combine to form hybrid subgenres, such as the melding of horror and comedy in the Evil Dead films. Other popular combinations include the romantic comedy, some vampire films, and the action comedy film. Alan Williams distinguishes three main genre categories: narrative, avant-garde and documentary. Genre movies are "commercial feature films which, through repetition and variation, tell familiar stories with familiar characters and familiar situations". Genre affects how films are broadcast on television, advertised, and organized in video-rental stores. One can also classify films by the setting, theme, topic, mood, format, target audience or budget. The setting is the environment where the story and action take place (e.g., a war film, a Western film, or a space-opera film). The theme or topic refers to the issues or concepts that the film revolves around (e.g., science-fiction film, sports film, or crime film). The mood is the emotional tone of the film (e.g., comedy film, horror film, or tearjerker film). Format refers to the way the film was shot (e.g., 35 mm, 16 mm or 8 mm) or the manner of presentation (e.g.: anamorphic widescreen). Additional ways of categorizing film genres may involve the target audience (for example: children's film, teen film or women's film) or by type of production (e.g., B movie, big-budget blockbuster or low-budget film, such as amateur film). Genre does not just refer to the type of film or its category; spectator expectations about a film, and institutional discourses that create generic structures also play a key role. Genres are not fixed; they change and evolve over time, and some genres may largely disappear (for example, the melodrama).