Black Mesa: Uplink

 "Black Mesa: Uplink is the recreation of the Half-Life demo (HL: Uplink) released by Valve in early 1999 with featured content that was scrapped from the original storyline."

  LINK
(mirrors)

How to Play it:
  1. Install Black Mesa Source. LINK
  2. Install Black Mesa: Uplink. 
  3. Open Black Mesa Source.
  4. Click on newgame and select Uplink (chapter 0).