This week, classic PC shooter Doom turned 21. So if you see someone in green slide up next to you at a bar and scream RIP AND TEAR, buy the guy a drink.
To celebrate, John Romero, one of the key figures involved in the creation of the game, shared a ton of artwork from Doom's development. You can check it out below. The collection includes everything from pencil-drawn sketches to animation tests. Most of it is pretty rough, but then, so was 1993.
Oh, and note that these images came from a dump that Romero put up for download yesterday; if you want to see some commentary for them, scroll down his Twitter feed.