Black Mesa, the long-anticipated fan remake of Half-Life, has officially gone live today after eight years in development. For those hearing about this mod project for the first time, it involves a ground-up rewrite of Half-Life using Valve's Source Engine, complete with new textures, physics, dialogues, and more.

The game will reintroduce players as Doctor Gordon Freeman in his journey through the Black Mesa Research Facility, along with the original cast of memorable characters and environments seen in Half-Life. Currently, Black Mesa only covers the first 80 percent or so of the original game, up to the Lambda Core level. The levels on alien world Xen aren't complete yet and will be added at a later date. Black Mesa's developers said the mod in its current form should give gamers "a complete 8-10 hour experience with a solid ending."

The 3.8GB Windows-only download is available for free but requires a copy of any Source Engine game installed on Steam in order to play it. Download servers are being hammered right now, but if you are having trouble starting a direct download from the project’s site, there’s also a torrent available.

This is not the first time we’ve seen Half Life running on the Source Engine. In 2004, Valve introduced a “digitally remastered version” of the critically acclaimed game named as Half Life: Source. But the community felt the advances in graphics and gameplay didn’t reflect what Source was actually capable of. Black Mesa is meant to address this with a much prettier version of Half-Life, and apparently Valve approves enough of the project that it has given it a spot in the first batch of Steam's Greenlight program.

Download: Black Mesa 1.0