ZZT

ZZT1) is text-mode based game creation system. It had a sequel known as Super ZZT, which was markedly less successful because the editor was hidden behind a commandline argument. Megazeux would later become game's de facto successor. Over the years there have been other attempts at making ZZT clones, such as ZIG, Bang!, Plastic, and heaven knows what else, but none of them ever caught on.

1) Named such so as to be at the bottom of alphabetical shareware lists. The name is not an abbreviation or acronym.