Today is the 15th anniversary of the release of Doom, the sci-fi first person shooter from id Software. On Dec. 10, 1993, the original shareware version was uploaded to a single FTP server. That's all it took for the game, about one space marine fighting an invasion from Hell on the moons of Mars, to spread across the world like wildfire on tens of millions of PC hard drives.
While the game wasn't the first FPS ever made, the release of Doom arguably launched the genre into the mainstream of gaming. The PC shareware version of the title became a massive hit with some people saying the DOS version of the shareware were installed on more PCs at one point than Microsoft's then current version of Windows.