Star Wars is a popular motion picture (1977) in the swashbuckling, 'space opera' tradition of Burroughs's Martian yarns. Morphologically diverse aliens feature prominently, notably in the bar scene, but for decorative purposes only. Although basically a western set in space, Stars Wars is unusual for its mystical element and, in particular, with the idea of an all-pervading "force" that can be harnessed by certain people for good or evil. The Empire Strikes Back (1980) and The Return of the Jedi (1983) completed the original trilogy which was followed by a series of "prequels" beginning in 1999.