The world of role-playing games began in the 1970s. The game "Dungeons & Dragons" (D&D) was a further adaptation of Gary Gygax's earlier medieval war game "Chainmail," and initially published by a company he helped to found, Tactical Studies Rules (later TSR, Inc.). D&D added the element of role-playing; players were now free to imagine the settings, characters, and events that were happening within a game. Basic D&D split in 1977, adding the more structured Advanced Dungeons & Dragons to the TSR line. The firm continued to publish both versions for some time, as well as other role-playing game series.