MUDs display a degree of openness unparalelled by most other virtual environments to date. MUDs have no storyline which must be played-out. Instead, MUDs begin with a world and objects built around a theme which, like a theme in a jazz composition, serves as a basic improvisational structure. Participant empowerment . Participants in MUDs have the ability to manipulate and change the environment within which they act.
Players can create objects, rooms, robots, etc. with algorithmic behaviors.
As the world evolves and grows, it becomes an increasingly interesting place to be. Symbolic vs. representational . MUDs are completely text-based, containing no graphics or sound. This has obvious disadvantages, but it has distinct advantages in terms of openness. Thus, MUDs require active participation in a way that graphical depictions of physical environments do not.