What Black Mesa is
Black Mesa is a reimagining of Half-Life, built by Crowbar Collective over 15 years and brought together in the Definitive Edition. You play Gordon Freeman, a theoretical physicist at the Black Mesa Research Facility, where a routine experiment goes wrong and opens the door to an interdimensional alien invasion. On top of that, a bloodthirsty military clean-up crew shows up. Your job is to fight through both and save the science team.
The single-player campaign runs for 19 chapters. You move through top-secret labs, harsh desert landscapes, abandoned railways, and across dimensions, including the new and expanded Xen levels. Along the way you carry an arsenal of military hardware, scientific prototypes, and the crowbar, against classic enemies rebuilt with new features and engaging AI. The Source Engine visuals, effects, soundtrack, and voice acting were all reworked for this version.
Playing it with friends
Black Mesa has multiplayer where you frag your friends across 10 maps from the Half-Life universe: Bounce, Gasworks, Stalkyard, Undertow, Crossfire, and others. It supports online PvP and cross-platform multiplayer, so your group can join up without worrying about everyone owning the same platform. Steam Achievements and Steam Trading Cards track what you unlock along the way.
Making your own content
The game includes level editor tools and the Black Mesa Source SDK, so you can build your own mods, models, and maps and share them on the Steam Workshop. There is a long-lived community workshop to pull from if you would rather play other people's work than make your own.
Before you start
The campaign is single-player, so the group experience lives in multiplayer and in swapping Workshop maps with each other. Controller support is partial, though Steam Input API Support is included, and captions are available in multiple languages. Steam Cloud handles saves, and Remote Play on Phone and Tablet lets someone tag in without installing it. Family Sharing covers access across accounts in the same family.