Half-Life 2 Episode 1 Trailer (2006)

As a standalone expansion released in 2006, this first-person shooter immediately continues the story of Gordon Freeman in war-torn City 17, focusing on stabilizing a core before evacuating citizens with Alyx Vance. Gameplay blends combat with physics puzzles, now featuring enhanced Source engine tech like improved facial animations. Though it continues the main plot, it requires no prior installation of the base game and offers a focused, high-stakes narrative chapter.