Greg Costikyan, also known as Designer X, is an American game designer and science fiction writer. Costikyan's career spans nearly all extant genres of gaming, including hex-based wargames, role-playing games, board games, card games, computer games, online games and mobile games. Several of his games have won Origins Awards. Costikyan was the game designer for the original version of Star Wars: The Roleplaying Game, and is credited under "original design" for its subsequent editions.