Space opera is a subgenre of science fiction that emphasizes space warfare, melodramatic adventure, interplanetary battles, as well as chivalric romance, and often risk-taking. Set mainly or entirely in outer space, it usually involves conflict between opponents possessing advanced abilities, futuristic weapons, and other sophisticated technology. The term has no relation to music, but is instead a play on the terms "soap opera" and "horse opera",[citation needed] the latter of which was coined during the 1930s to indicate clichéd and formulaic Western movies. Space operas emerged in the 1930s and they continue to be produced in literature, film, comics, and video games.