xonotic!

if you ever played Quake or Unreal Tournament and won't mind playing something like this on the weekend, I suggest Xonotic. That's an open-source FPS!

https://xonotic.org/

As far as I understood, back in the day people wanted to have free Quake. Ergo a mod called Nexuiz was born, then after a split from developers Xonotic was born. Xonotic has a FANTASTIC electronic soundtrack and I suggest just reading their website and checking it out.

1.5 gigabyte of download gives you a fast-paced fun shooter than you can jump into after some time. Both singleplayer and multiplayer