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.
Early history of video games
Following the 1947 invention of the cathode-ray tube amusement device, the earliest known interactive electronic game as well as the first to use an electronic display, the first true video games were created in the early 1950s. Initially created as technology demonstrations, such as the "Bertie the Brain" and Nimrod computers in 1950 and 1951, video games also became the purview of academic research. A series of games, generally simulating real-world board games, were created at various research institutions to explore programming, human–computer interaction, and computer algorithms. These include "OXO" and Christopher Strachey's draughts program in 1952, the first software-based games to incorporate a CRT display, and several chess and checkers programs. Possibly the first video game created simply for entertainment was 1958's "Tennis for Two", featuring moving graphics on an oscilloscope. As computing technology improved over time, computers became smaller and faster, and the ability to work on them was opened up to university employees and undergraduate students by the end of the 1950s. These new programmers began to create games for non-academic purposes, leading up to the 1962 release of "Spacewar!" as one of the earliest known digital computer games to be available outside a single research institute.