Multi-User Dungeon, or MUD (referred to as MUD1, to distinguish it from its successor, MUD2, and the MUD genre in general) is an early MUD and one of the oldest examples of a virtual world in existence.
When the first fully-assembled Apple II systems began shipping in June 1977, a single tape cassette was included, containing demonstration programs written in Integer BASIC by Steve Wozniak. Notably, one side of the tape held the first Apple II version of Breakout, inspired by Wozniak's own work on Atari's blockbuster arcade game of the same title.