Black Mesa (formerly Black Mesa: Source) is a Half-Life 2 total conversion remaking of Valve Software's award-winning PC game, Half-Life.
Utilizing the Source engine, Black Mesa will reintroduce the player as Doctor Gordon Freeman, along with the original cast of memorable characters and environments seen in Half-Life. Black Mesa was built and founded on the basis that Half-Life: Source didn't fully live up to the potential of a Source engine port of Half-Life. As such, Black Mesa was founded to fully reconstruct the Half-Life universe utilizing Source to its fullest potential in terms of art detail, level sizes and code features.
It should be noted that the project is being built from the ground up and is not a simple port of Half Life maps and models into the Source Engine. The idea is to remake the storyline used in Half Life into a new polished Source Engine version with new models, maps, soundtrack, voice acting and textures.
This total conversion will not require Half-Life: Source to play - only a copy of any Source Engine game installed on Steam. For more details, check the System Requirements.
From the Black Mesa Wiki
Requires only a FREE installation of the Source Sdk Base 2007!Prepare for an experience that you will find Nostalgic, exciting and fresh. Black Mesa is a re-envisioning of Valve Software's seminal game Half-Life. You will re-visit the inaugural role of Gordon Freeman and his memorable journey through the Black Mesa Research Facility.
Expect tremendously detailed environments to explore, a huge cast of characters and experimental weaponry. All-new music, voice acting, choreography and added dialogue give way to a more expansive and immersive experience than ever before. In a nutshell, play Half-life the way we think it was meant to be played!
Play for FREE! You need not purchase anything! 8-10 Hours of single-player gameplay, up to the Lambda Core chapter. Feast your eyes on over 2,000 custom Models and 5,000 custom textures – more than HL2!
Experience over 2,000 choreographed scenes and over 6,500 lines of dialogue from all new voice acting! Subtitles in English, Italian, Spanish, Norwegian, German, and Finnish!
Immerse yourself in an all new soundtrack and over 2,300 custom sound effects! Feel the impact of custom systems such as the Face Creation System, Custom Gib System, Deathcam and more.