anchor.diff:  
     environment.systemPackages = with pkgs; [
       firefox  # web browser
  -    home-manager  # user environment configuration
       git  # version control system
       vim  # text editors
       wget  # retrieve files from the web
       zsh  # better than bash
     ];
  -
  -  # make home-manager use global configs and install paths (as opposed to user-specefic ones)
  -  home-manager.useUserPackages = true;
  -  home-manager.useGlobalPkgs = true;
   
     users.users.perlinm = {
       isNormalUser = true;
  
positive.code:     extraGroups = [ "wheel" "sudo" "networkmanager" ];
      shell = pkgs.zsh;
    };
  }
  
negative.code:     # keyboard layout
      layout = "us";
      xkbVariant = "colemak";
      autoRepeatDelay = 200;  # delay before a key repeats, in milliseconds
      autoRepeatInterval = 60;  # delay between repeat strokes, in milliseconds
  
      # display (login) and desktop managers
      displayManager.gdm.enable = true;
  