Castle

Castle was created from 1973 to 1974 by Peter Langston as the first game to use his text adventure scripting language, Wander.

Wander was originally created in HP Time-Shared BASIC, likely on an HP 2000, in 1973. It was converted to C in 1974 and was released it on a mainframe running UNIX V5 at Harvard University later that year, predating the first release of Colossal Cave Adventure by a year.  Work on it continued until 1980 when it was released on a PSL Games collection for Unix.

It was thought lost until an interactive fiction enthusiast, with the handle "ant", contacted Peter Langston in 2015. The 1980 version of the Wander game creation system was discovered in an e-mail archive by Lou Katz, but it only contained a demo version of Colossal Cave Adventure converted to Wander. The entire 1980 version was discovered when Doug Merrit found the files included with the PSL Games collection.