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.
Everyone's A Wally
"Everyone's a Wally" was the first arcade adventure game to feature multiple playable characters - a revolutionary feature at the time. Players began in control of Wally (a builder and handyman), but could switch to Wilma (his wife), and their friends Tom (a punk plumber), Dick (a dodgy bricklayer) and Harry (a hippie electrician) - these last three names drawn from the placeholder phrase Tom, Dick and Harry. Herbert (their baby son) also appeared in the game as a mobile hazard NPC. The player cannot freely change character; the player begins in control of Wally and in order to switch must be on the same screen as the desired character. Those not being controlled by the player wander randomly around the map controlled by extremely simple AI - another feature that at the time had never been seen before. Lives and health (called "endurance") were tracked independently for each character, but the game ended if any character died.