There is an almost fractal quality to the history of id Software, in that the closer you look at it, the more games seem to appear. The studio's first official game is Commander Keen in Invasion of the Vorticons, but prior to that is a weird transition period where the creators of Doom were still partly tied to its previous employer, Softdisk.
It was during this period that id Software's four founders developed Dangerous Dave in the Haunted Mansion, a side-scrolling shooter released in late 1990. Sequel to 1988's Dangerous Dave in the Deserted Pirate's Hideout, which was created exclusively by John Romero, it's generally regarded as the best in the series, notable for how it let you blast zombies into chunky gibs with your shotgun—a shocking display of violence that would soon be massively eclipsed by id Software's first-person shooters.
