add gamemode

system/configuration.nix

@@ -2,7 +2,10 @@
 # your system.  Help is available in the configuration.nix(5) man page
 # and in the NixOS manual (accessible by running ‘nixos-help’).
 { config, pkgs, inputs, ... }: {
-  imports = [ ./media-packages.nix ];
+  imports = [
+    ./gamemode.nix
+    ./media-packages.nix
+  ];
   packages.media-packages.enable = true;
 
   # Bootloader.

system/gamemode.nix

@@ -0,0 +1,21 @@
+{ config, pkgs, inputs, ... }: {
+  programs.gamemode.enable = true;
+  programs.gamemode.enableRenice = true;
+  programs.gamemode.settings = {
+    general = {
+      renice = 10;
+    };
+
+    # Warning: GPU optimisations have the potential to damage hardware
+    gpu = {
+      apply_gpu_optimisations = "accept-responsibility";
+      gpu_device = 0;
+      amd_performance_level = "high";
+    };
+
+    custom = {
+      start = "${pkgs.libnotify}/bin/notify-send 'GameMode started'";
+      end = "${pkgs.libnotify}/bin/notify-send 'GameMode ended'";
+    };
+  };
+}