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.
Roguelike
The creation of roguelike games came from hobbyist programmers and computer hackers, attempting to create games for the nascent computer field in the early 1980s, particularly influenced by the 1975 text adventure game "Colossal Cave Adventure" (often simply titled "Adventure"), and from the high fantasy setting of the tabletop game "Dungeons & Dragons". Some elements of the roguelike genre were present in dungeon crawlers written for the PLATO system. This includes "pedit5" (1975) believed to be the first dungeon crawl game, and featured random monster encounters, though only used a single fixed dungeon level. "pedit5" inspired similar PLATO-based dungeon crawlers "dnd" (1975), "orthanc" (1978), "Moria" (1978), and "avatar" (1979). It is unclear if these PLATO games inspired the roguelike genre as there is no evidence that the early roguelike creators had access to these games. The core roguelike games were developed independently of each other, many of the developers not learning about their respective projects until several years after the genre took off.