Modern 'Quake engines' like Quakespasm, Mark V, FTE, and ezQuake are still being developed though, and so the features and behaviors of the newest versions of these engines may be somewhat different than what these guides describe now.
Since Quake is a classic game, a lot of the stuff in these guides doesn't need to change. Not a lot of game time, and what I do have goes into things other than guide-writing these days. Family stuff, etc., you know how it goes. I haven't maintained these guides in a while. I'm putting this generic update on all my Quake guides here on Steam, just as an FYI:
