ZZT

ZZT is a 1991 action-adventure puzzle video game and game creation system developed and published by Potomac Computer Systems for MS-DOS. It was later released as freeware in 1997. It is an early game allowing user-generated content using object-oriented programming. Players control a smiley face to battle various creatures and solve puzzles in different grid-based boards in a chosen world. It has four worlds where players explore different boards and interact with objects such as ammo, bombs, and scrolls to reach the end of the game. It includes an in-game editor, allowing players to develop worlds using the game's scripting language, ZZT-OOP.

The game was designed by mechanical engineering student Tim Sweeney in roughly six to nine months. It was built from a text editor conceived in 1989 to build a better editor for Pascal, after he disliked editors that came with other programming languages. During development, he experimented with adding creatures and characters. He built boards that grew into worlds and refined the editor he used to create his own gameswhile studying at university. Initially, he made the game for himself, but after positive reception from his friends and neighbors, and seeing the potential for making a profit by releasing the game under shareware, he released it publicly. He marketed the game by distributing it across shareware vendors and bulletin board systems, earning money through mail orders for registered worlds.