Black Mesa, formerly known as Black Mesa: Source, is a remake of Valve's very first game. It makes use of the Source engine which, while hardly cutting edge, does allow for the game to look vastly improved over the original. Valve itself ported Half-Life to the Source engine years ago, though it was hardly a major overhaul. Black Mesa takes things a significant step further: everything has been built from scratch, including not only new and improved graphics, but also an excellent new soundtrack, new voice acting, larger map sizes, and more. The game both looks and sounds better than Half-Life: Source, and really, it's superior in most every way. The AI, particularly that of friendlies, is the one glaring weak point from my experience; it was always a crapshoot whether it would attack enemies, and it never made much of an effort to avoid being attacked.