It's always nice to see a mod progress from humble beginnings to its own Steam product page, and Estranged is fully deserving of the achievement. Alan Edwardes' spooky, puzzle-filled FPS plays and looks like a first-person Alan Wake, and it's an excellent deviation from standard run-and-gun zombie-fragging with its supernatural twists and an atmospheric sense of foreboding. The first act is available on Steam as a free download independent of any Source-based game, so you won't need Half-Life 2 to jump in and start exploring.
After months of alpha releases, Estranged, a first-person shooter/exploration mod for the Source Engine, has finally entered beta! With new (and reworked) maps, new voice work, and new models, Estranged casts you as a fisherman stranded on a mysterious island where many of the residents have gotten a bit bitey. Solve physics puzzles, talk to a few oddball locals, and engage in occasional bouts of armed combat with zombie-types and guards as you explore the mod's first three-chapter act. You don't even need Half-Life 2 to run it, only the free download of Source SDK Base 2013.
The only thing missing from Alan Edwardes' Half-Life 2 mod Estranged is a cryptic introduction narrated by Rod Serling, possibly with a door flying into your face from a starry sky. But Estranged's "key of imagination" still unlocks plenty of mystery involving a wrecked ship, a puzzling island, its eccentric inhabitants, and a moonlit beach.