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.
Odyssey: The Compleat Apventure
Although primitive by today's standards, "Odyssey" was considered cutting-edge for its time, making use of the Apple II's two graphics modes (high-resolution and low-resolution), and text. The game was written in Integer BASIC and was one of the first microcomputer games to be created using multiple programs, requiring floppy disc activation and access mid-game. (This feature, however, led to a way in which the player could cheat: by removing the disk when the computer required access, a cursor flashes on screen; typing "goto 770" would fool the computer into thinking that the player had just opened up a treasure box. This is one of the earliest known examples of a cheat code.) Prior to this, most games were self-contained, single programs; Odyssey was split into several different programs and took up an entire disk. The game also made use of rudimentary sound effects.