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.
Easter egg (media)
In addition to Robinett's name appearing in "Adventure" (1979), there are many other instances where the Easter egg idea has been implemented. The first text adventure game, "Colossal Cave Adventure" (1976), from which "Adventure" was fashioned, included several secret words. One of these was "xyzzy", a command which enabled the player to move between two points in the game world. In 2004, an Easter egg displaying programmer Bradley Reid-Selth's surname was found in "Video Whizball" (1978), a game for the Fairchild Channel F system. According to research by Ed Fries, the first known Easter egg in an arcade game was in "Starship 1" (1977), programmed by Ron Milner. By triggering the cabinet's controls in the right order, the player could get the message "Hi Ron!" to appear on the screen. Fries described it as "the earliest arcade game yet known that clearly meets the definition of an Easter egg". The existence of this Easter egg wasn't published until 2017, leading Fries to suggest that, as more than one hundred arcade games predate "Starship 1", earlier Easter eggs may still be undiscovered. Fries noted that some Atari arcade cabinets were resold under the Kee Games label and included changes to the hardware that would make the game appear different from the Atari version. "Anti-Aircraft II" (1975) included a means to modify the circuit board to make the airplanes in the game appear as alien UFOs. Fries surmised that this feature may have been intended for a Kee Games release. For this reason, and because it required a hardware modification, Fries questioned whether it met the definition of an Easter egg.