After 15 long years, Black Mesa's ambitious retelling of Half-Life finally wrapped up with a 1.0 release this March. Except, not quite, because Crowbar Collective announced they'd be working on a 1.5 "Definitive Edition" of the fan remake before they'd even pushed the finished thing out the door.
Seven months of relative silence later, the Definitive Edition has surfaced with an exhaustive blog post explaining the changes. You can see where they're coming from, too—Black Mesa was a project spanning 15 years, with a literal decade separating some of its levels and features.
The bulk of this new beta, then, is dedicated to bringing some of the game's earliest maps in visual line with its gorgeous Xen levels, the last to be added to Black Mesa before release. Most of the outdoor desert spaces have been given a sweeping art pass with brand new models, textures, and some subtle colour correction.
Back indoors, the Power Up chapter now has a new sequence for turning the lights back on, littering the location with flickering dynamic lights. On A Rail, already heavily modified from its original Valve layout, has substantially reworked the silo to give the rocket "the respect it deserves."
The beta also adds a host of gameplay changes, shifting enemy placements and smoothing out collision detection. In what may seem a controversial move, Definitive Edition also adds Half-Life 2-style supply boxes containing health, batteries or both.
Finally, Steam Workshop support has been improved to both expand the kinds of mods that can be made, and make it easier to filter through the Workshop's collection. Full patch notes for Black Mesa 1.5 can be found on the Steam Announcement post.
The Black Mesa: Definitive Edition Beta can be accessed by selecting "public-beta" from the game's Steam dropdown. If you've not jumped aboard the tram, Black Mesa is currently 50% off in the Steam Halloween sale.