Between the introduction of internet MUDs
and before there were dedicated MMORPGs on PCs, there were Bulletin Board System door games. A "door" is any external program designed to be launched from a BBS, and transmitted across the connection. A typical user "dialed in" with computer and modem, and launched a door game from a menu. Upon quitting, the user returned to the BBS menu.
Methods of Play
Most games were primarily text-based with ASCII
and ANSI (colored and/or animated) based graphics, and could only allow one user per connection to play concurrently. A daily time or turn limit allowed all players an equal chance at progressing. Modern MMOs use a Fatigue System to similar effect.
Very popular door games often made use of a customized graphical front-end program (e.g. "Ansiterm") that the player could download and launch while connected to the BBS. This gave the player all of the game's resources locally, ensuring a smoother experience not dependent on connection speed, and could even offer full graphics and sound.