The game is free software, so no purchasing is required.
Under Windows you just have to unpack the zip archive.
It is known, that the game does not work properly when trying to use 4K resolution out of the box. The problem can be mitigated by changing the properties of the xonotic.exe to not use Windows' scaling.
en/games/xonotic.txt · Last modified: 2021-07-11-22-43 by 7saturn