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.
Visual novel
Some of Japan's earliest adventure games were erotic bishōjo games developed by Koei. In 1982, they released "Night Life", the first commercial erotic computer game. It was a graphic adventure, with sexually explicit images. That same year, they released another erotic title, "Danchi Tsuma no Yūwaku" ("Seduction of the Condominium Wife"), which was an early adventure game with colour graphics, owing to the eight-color palette of the NEC PC-8001 computer. It became a hit, helping Koei become a major software company. Other now-famous companies such as Enix, Square and Nihon Falcom also produced similar erotic games in the early 1980s before they became famous for their role-playing video games. While some early erotic games meaningfully integrate the erotic content into a thoughtful and mature storyline, others often used it as a flimsy excuse for pornography. The Japanese game Pai Touch! involves the protagonist gaining the ability to change the size of girls' breasts, and the adventures that ensue in trying to choose which girl to use the power on the most.