The Lurking Horror is an interactive fiction game released by Infocom in 1987. The game was written by Dave Lebling and inspired by the horror fiction writings of H. P. Lovecraft (including his Cthulhu Mythos). Like most of Infocom's games, it was released for several platforms simultaneously thanks to the Z-machine. The original release included versions for DOS, the Apple II, Atari ST, Atari 8-bit family and Commodore 64. Later, it was ported to the Amiga with the addition of sound effects, making it the first title with that feature. The effects would play at appropriate times in the game in an effort to intensify the horror atmosphere. This marked one of the few major additions to the Z-machine with the exception of graphics; traditionally, Infocom had eschewed such changes in favor of expanding the parser capacity and overall size of game files. It was Infocom's 26th game; Infocom rated it as "Standard" in terms of difficulty. Lurking Horror was the only horror game ever released by Infocom.