Since the release of Black Mesa, modders have been bending and shaping its spruced up Half-Life assets to create Source upgrades of every one of the game's expansions , demos and curios . But mod group Tripmine Studios are attempting to go it alone, Sourcing up Gearbox's Opposing Force expansion entirely from scratch. The name of their project? Operation Black Mesa. Wait, what?

Confusing name aside, it's looking like an accomplished upgrade of Adrian Shephard's adventures through the bowels of Black Mesa. It's certainly looks more muted than the other Black Mesa's visual shock and awe, but the lighting seems to nicely capture the underground claustrophobia of HL1's dated engine.

According to Tripmine's team leader Antonín Žoha, the multiplayer portion of the mod is due to arrive in Q1 2014, and will bring "classic modes like deathmatch, team deathmatch, capture the flag and one brand new game mode for people who are also looking for something new." There's currently no release date for the singleplayer portion.

Despite the wait, you can already vote for Operation Black Mesa on Steam Greenlight . More details are available on the project's ModDB page . Also on ModDB are details of Tripmine's other expansion overhaul, Guard Duty , a Blue Shift remake.

More Operation Black Mesa screenshots below.