// Background Size
// Set the size of background images using px, width and height, or percentages
//  - percentages are relative to the background-origin (default = padding-box)
//  - mixin defaults to "100% auto"

//  override constants to change defaults
!default_background_size ||= 100% "auto"

=background-size(!size = !default_background_size)
  background-size= !size
  -webkit-background-size= !size
  -o-background-size= !size
  -khtml-background-size= !size
  -moz-background-size= !size