Pretty good! When it comes to the feeling, the atmosphere, and the total lack of concern for story, this is the most faithful to the original Quake of any of the expansions I've played so far. The map design and enemy encounters are much different, borrowing the abstract approach of Quake 1 but little else. A lot of maps are designed symmetrically, with multiple tidy loops that all bring you back to the beginning. Most maps have at least one enemy encounter that is designed to be overwhelming, nearly impossible to survive without fleeing. I imagine this is frustrating for the type of Quake completionists who feel the need to kill every enemy in every map, but once I realized that was not going to be possible for most of these maps I actually found it quite freeing. The whole experience is pretty interesting, like playing a Quake that's informed by 20 years of genre evolution. It doesn't always work, but it's never boring.