anchor.diff:      };
   
       activeOpacity = mkOption {
  -      type = types.str;
  +      type = floatBetween "0.0" "1.01";
         default = "1.0";
         example = "0.8";
         description = ''
  -        Opacity of active windows.
  +        Opacity of active windows (number in range 0.0 - 1.0).
         '';
       };
   
       inactiveOpacity = mkOption {
  -      type = types.str;
  +      type = floatBetween "0.1" "1.01";
         default = "1.0";
         example = "0.8";
         description = ''
  -        Opacity of inactive windows.
  +        Opacity of inactive windows (number in range 0.1 - 1.0).
         '';
       };
   
       menuOpacity = mkOption {
  -      type = types.str;
  +      type = floatBetween "0.0" "1.01";
         default = "1.0";
         example = "0.8";
         description = ''
  -        Opacity of dropdown and popup menu.
  +        Opacity of dropdown and popup menu (number in range 0.0 - 1.0).
         '';
       };
   
       opacityRules = mkOption {
         type = types.listOf types.str;
         default = [];
  -      description = ''
  -        Opacity rules to be handled by compton.
  +      example = [
  +        "95:class_g = 'URxvt' && !_NET_WM_STATE@:32a"
  +        "0:_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'"
  +      ];
  +      description = ''
  +        Rules that control the opacity of windows, in format PERCENT:PATTERN.
         '';
       };
   
       backend = mkOption {
  -      type = types.str;
  +      type = types.enum [ "glx" "xrender" ];
         default = "glx";
         description = ''
           Backend to use: <literal>glx</literal> or <literal>xrender</literal>.
  
positive.code:     };
  
      fadeDelta = mkOption {
        type = types.int;
        default = 10;
        example = 5;
        description = ''
  
negative.code:     };
  
      vSync = mkOption {
        type = types.enum [
          "none" "drm" "opengl"
          "opengl-oml" "opengl-swc" "opengl-mswc"
        ];
        default = "none";
        example = "opengl-swc";
        description = ''
          Enable vertical synchronization using the specified method.
          See <literal>compton(1)</literal> man page an explanation.
        '';
      };
  
      refreshRate = mkOption {
        type = types.addCheck types.int (x: x >= 0);
        default = 0;
        example = 60;
        description = ''
  