Blanket Doom is a mod for Doom, created by TheDrakeRaider.
Description (by authors’ own words)
A combination of Doom 1's maps into single levels. I played Doom as 1 level, and Doom:One, and both were good. But neither were what I wanted. I wanted each episode as a single map, and each map to play like a full mission, rather than a short campaign. So I took matters into my own hands, and built my own mod. Which is here. Only works on ZDoom based source ports. All credit to Randy Heit, CodeImp, Graf Zahl, and to id Software, who's maps these actually are, in heart. Though I used them very differently than they. Enjoy, tell me how you like it!
To launch the mod use GZDoom.