anchor.diff:      };
   
       fadeSteps = mkOption {
  -      type = types.listOf types.str;
  +      type = pairOf (floatBetween "0.01" "1.01");
         default = [ "0.028" "0.03" ];
         example = [ "0.04" "0.04" ];
         description = ''
           Opacity change between fade steps (in and out).
  +        (numbers in range 0.01 - 1.0)
         '';
       };
   
  
positive.code:     };
  
      shadowOpacity = mkOption {
        type = types.str;
        default = "0.75";
        example = "0.8";
        description = ''
          Window shadows opacity (number in range 0 - 1).
        '';
      };
  
  
negative.code:       inactive-opacity = ${cfg.inactiveOpacity};
        menu-opacity     = ${cfg.menuOpacity};
  
        opacity-rule = [
          ${opacityRules}
        ];
  
        # other options
        backend = ${toJSON cfg.backend};
  