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 heaps 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.