immersive environment, virtual worlds typically rely on mentally and emotionally engaging content which gives rise to an immersive experience. Maze War was the first networked, 3D multi-user first person shooter game. Maze introduced the concept of online players in 1973–1974 as "eyeball 'avatars' chasing each other around in a maze." It was played on ARPANET, or Advanced Research Projects Agency Network, a precursor to the Internet funded by the United States Department of Defense for use in university and research laboratories. The initial game could only be played on an Imlac, as it was specifically designed for this type of computer. The first virtual worlds presented on the Internet were communities and chat rooms, some of which evolved into MUDs and MUSHes. The first MUD, known as MUD1, was released in 1978. The acronym originally stood for Multi-User Dungeon, but later also came to mean Multi-User Dimension and Multi-User Domain. A MUD is a virtual world with many players interacting in real time. The early versions were text-based, offering only limited graphical representation and often using a Command Line Interface. Users interact in role-playing or competitive games by typing commands and can read or view descriptions of the world and other players. Such early worlds began the MUD heritage that eventually led to massively multiplayer online role-playing games, more commonly known as MMORPGs, a genre of role-playing games in which a large number of players interact within a virtual world. Some prototype virtual worlds were WorldsAway, a two-dimensional chat environment where users designed their own avatars; Dreamscape, an interactive community featuring a virtual world by CompuServe; Cityspace, an educational networking and 3D computer graphics project for children; and The Palace, a 2-dimensional community driven virtual world. However, credit for the first online virtual world usually goes to Habitat, developed in 1987 by LucasFilm Games for the Commodore 64 computer, and running on the Quantum Link service (the precursor to America Online). In 1996, the city of Helsinki, Finland with Helsinki Telephone Company (since Elisa Group) launched what was called the first online virtual 3D depiction intended to map an entire city. The Virtual Helsinki project was eventually renamed Helsinki Arena 2000 project and parts of the city in modern and historical context were rendered in 3D. In 1999, Whyville.net the first virtual world specifically for children was launched with a base in game-based learning and one of the earliest virtual