In 1998, Valve Software changed the video game landscape forever with Half-Life, an influential horror-fueled first-person shooter that pushed the limits of technology and video game narratives. Six years later, they expanded even further with Half-Life 2. Two years after that, they released two self-contained "episodes" continuing the Half-Life 2 story, with the promise of a third on the horizon. And then... silence. No new Half-Life game, tons of fan demand. Now, finally, out of nowhere, Valve has tweeted out the next chapter in the saga. It's called Half-Life: Alyx, named …