Doom - one of the most influential video games ever made - is 20 years old.
ID Software's classic and iconic first-person shooter was first uploaded to a server at the University of Wisconsin late on 9 December, 1993 - and it's fair to say that quite quickly it changed video games forever.
In the game, the player has to hunt through mazes for keys and solve puzzles while battling raging hordes of monsters, demons and zombies.
Looking back, it might not immediately seem that groundbreaking: Doom was not the first video game to use a first-person 'behind the gun' viewpoint, after all, and certainly not the first to use 3D-like graphics, maze hunts or most of its other key mechanics.
But nothing before Doom managed to put those elements together in a way that was so fast, so convincing - and so scary. For it wasn't the action alone, but rather the suspense and genuine fear the game inspired, that changed the industry and won legions of fans.
Other key factors in its success ranged from its 'shareware' revenue model - in which free copies of the first levels were given away to encourage players to buy the full game - to its expandability via level editors and its simple multiplayer "Deathmatch" mode, which went on to influence everything up to the latest Call of Duty and Battlefield games.
Needless to say, Doom was a huge success, recording millions of sales and gaining a release on virtually every games console around, including the Game Boy Advance. Being able to run the game became essentially synonymous with usefulness as a computing device.
To read more about Doom, check out this amazing write-up of the game's history. We also have a review of the old game (as well as Doom 3) here. But perhaps the best way to remember it is to watch some of its best moments: