Black Mesa is a fan-made remaster that brings all the Half-Life gameplay elements into the new engine without adding any new enemies, characters or weapons to the game. At the same time, Black Mesa also uses its own objects, such as new game models and independent music.

The mod was called Black Mesa: Source, but at the request of Valve it was renamed Black Mesa. Work on the project continued, and release dates were regularly delayed, until an incomplete release of the game was created in 2012, which was still missing the final story chapters dedicated to the world of Xen.