=background($values...)
  $background-values: ()
  @each $value in $values
    $background-value: ()
    $background-color: ()
    $background-image: ()
    $background-gradient: ()
    $background-position: ()
    $background-repeat: ()
    $background-attachment: ()
    $background-size: ()
    $background-clip: ()
    @each $property in $value
      @if background_color($property)
        $background-color: $property
      @else if background_image($property)
        $background-image: $property
      @else if background_gradient($property)
        $background-gradient: $property
      @else if background_position($property)
        $background-position: $property
      @else if background_repeat($property)
        $background-repeat: $property
      @else if background_attachment($property)
        $background-attachment: $property
      @else if background_size($property)
        $background-size: background_size_value($property)
      @else if background_clip($property)
        $background-clip: $property
      @if background-size != () and $background-position == ()
        $background-position: (left top)
      $background-value: $background-color $background-image $background-gradient $background-position $background-size $background-repeat $background-attachment $background-clip
    $background-values: append($background-values, $background-value, comma)
  background: $background-values