Thriller is a genre of fiction, having numerous, often overlapping subgenres. Thrillers are characterized and defined by the moods they elicit, giving viewers heightened feelings of suspense, excitement, surprise, anticipation and anxiety. Thrillers generally keep the audience on the "edge of their seats" as the plot builds towards a climax. The cover-up of important information is a common element. Literary devices such as red herrings, plot twists, and cliffhangers are used extensively. A thriller is usually a villain-driven plot, whereby they present obstacles that the protagonist must overcome.