Dark Interval is a restoration/revision mod that lets you play Half-Life 2 as it could have been. Using Valve's early concepts, we're creating new maps, models, textures, and custom dialogue. The mod is released in episodes, the most recent being Dark Interval: Part I - an intro chapter to the bigger story.
looks like the old Half Life 2 Beta, which in my utmost opinion was the best theme
The mod is based around the Half Life 2 Beta.