Open world
There is no consensus on what the earliest open world game is, due to differing definitions of how large or open a world needs to be. Ars Technica traces the concept back to the free-roaming exploration of 1976 text adventure game "Colossal Cave Adventure", which inspired the free-roaming exploration of "Adventure" (1980), but notes that it wasn't until 1984 that what "we now know as open-world gaming" took on a "definite shape" with 1984 space simulator "Elite", considered a pioneer of the open world; Gamasutra argues that its open-ended sandbox style is rooted in flight simulators, such as SubLOGIC's "Flight Simulator" (1979/1980), noting most flight sims "offer a 'free flight' mode that allows players to simply pilot the aircraft and explore the virtual world". Others trace the concept back to 1981 CRPG "", which had a free-roaming overworld map inspired by tabletop RPG "Dungeons & Dragons". The overworld maps of the first five "Ultima" games, released up to 1988, lacked a single, unified scale, with towns and other places represented as icons; this style was adopted by the first three "Dragon Quest" games, released from 1986 to 1988 in Japan.
Gamebook
Solitaire adventures were a parallel development. This type of book is intended to allow a single person to use the rules of a role-playing game to experience an adventure without need of a referee. The first role-playing game solitaire adventures to be published were those using the "Tunnels and Trolls" system, beginning with the book "Buffalo Castle" in 1976, making "Tunnels and Trolls" the first role-playing game to support solitaire play. Flying Buffalo released 24 solo adventure books (plus several pocket size adventures) in the period 1976–1993. A number of the adventures are still in print today. They were very successful among players of role-playing games and inspired many imitators.