The Waterfront

The Waterfront (WTRFRONT.WAD) is a level created by Scott F. Crank in May 1995. It is maybe the earliest level to deliberately exploit the ghost monster bug, which its text file calls the "arch-vile bug." The author provided an additional text file documenting how ghost monsters are created, and how they can be killed only by rockets (or infighting), with a demo illustrating the technique.