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.
Adventure (Atari 2600)
As the first action-adventure video game and first console fantasy game, "Adventure" established its namesake genre on video game consoles. In addition to being the first graphical adventure game on the Atari 2600 console, it is the first video game to contain a widely known Easter egg, and the first to allow a player to use multiple, portable, on-screen items while exploring an open-ended environment, making it one of the first examples, even as small and primitive as it is, of an open world game. The game has been voted the best Atari 2600 game in numerous polls, and has been noted as a significant step in the advancement of home video games. "GamePro" ranked it as the 28th most important video game of all time in 2007. In 2010, "1UP.com" listed it as one of the most important games ever made in its "The Essential 50" feature. "Entertainment Weekly" named "Adventure" as one of the top 10 games for the Atari 2600.