[PC] Steam - Black Mesa Definitive Edition - $14.47 (was $28.95) - Steam

Great price for a highly rated game.

From the website:

Relive Half-Life
Black Mesa is the fan-made reimagining of Valve Software’s Half-Life.

Black Mesa: Definitive Edition
Update 1.5 brings together all the improvements to graphics and gameplay across 15 years of development to create the final version of Black Mesa. There has never been a better time to pick up the crowbar and play!
Single Player Campaign
You are Gordon Freeman, a theoretical physicist at the Black Mesa Research Facility. When a routine experiment goes horribly wrong, you must fight your way through an interdimensional alien invasion, and a bloodthirsty military clean-up crew in order to save the science team… and the world!

Features

A completely reimagined and refined single player campaign, including all new and expanded Xen levels

19 chapters of fighting through top-secret labs, running atop harsh desert landscapes, sneaking into abandoned railways, and leaping across dimensions

Mind-Blowing graphics and effects, never before seen on the Source Engine

Face off against an army of classic enemies, updated with new features and engaging AI

Wield an arsenal of military hardware, scientific prototypes, and the iconic crowbar through incredibly detailed environments

The all-new soundtrack and voice acting create a more immersive experience than ever before
50 Fun and challenging achievements

Multiplayer

Frag your friends across 10 iconic maps from the Half-Life universe, including:
Bounce
Gasworks
Stalkyard
Undertow
Crossfire

Workshop
Create your own mods, models, and maps with the Black Mesa Source SDK, then share it with the community on the Steam Workshop.

Steamworks
Collect the full set of trading cards, backgrounds, emoticons, and achievements! Featuring Steam Cloud, Steam Workshop, closed captions in multiple languages and full controller support.

Enjoy!