Star Wars: The Old Republic is a science fiction MMORPG set in the Star Wars universe between the events of Star Wars: Knights of the Old Republic and the Star Wars films. Players choose to side with either the Sith Empire or Galactic Republic and may separately choose to use the light or dark side of the Force. Players' choices affect their available missions and storylines. They may interact and build relationships with companion non-player characters, who can complete passive Crew Skills to gather and craft items. Character classes are not limited to one group role and may be customized on-the-fly to accommodate the situation. Star Wars: The Old Republic is one of the first few MMORPGs to use a cover system in combat.