{ pkgs, ... }: {
  nixpkgs.overlays = [
    (self: super: {
      tibia = super.tibia.overrideAttrs (old: {
        src = super.fetchurl {
	  url = "https://correct-url.example.com/tibia.tar.gz";
	  sha256 = "sha256-..."; 
	};
      });
    })
  ];
  # paczki
  environment.systemPackages = with pkgs; [
    tibia

  ];
}