Black Mesa, the fan-created re-imagining of Valve's landmark shooter Half-Life, is now available on Steam Early Access.
The move to Steam Early Access, the developer said today, will be "a tool for allowing our community to participate in the final phase of Black Mesa's development."
"In addition, our ambitions go beyond the original Xen chapters found in Half-Life," developer Crowbar Collective said. "We have a standard of quality that we have to achieve. Early Access allows us to commit resources to bring you the remaining chapters with the quality that you expect."
The Early Access version of Black Mesa, which has been in development in some form since 2004, costs $19.99. It includes more than 10 hours of the game's single-player campaign, the developer says, as well as multiplayer — deathmatch and team deathmatch — on six re-imagined maps from Half-Life: Bounce, Gasworks, Lambdabunker, Stalkyard, Subtransit and Undertow.
As for the game's remaining single-player content, the notoriously unenjoyable levels set on an alien world, the developer hopes to "improve upon it to make it an enjoyable and memorable experience."
The legacy version of Black Mesa is still available to download for free via the game's official website.
For more on the Black Mesa project read Polygon's interview with the developer from 2012.