/// Create a transparent & colored overlay
//// @group Overlays
/// @param {color} $color [none] - color overlay
@mixin overlay($color) {
  @include square(100%);
  position: fixed;
  top: 0;
  left: 0;
  z-index: 10000;
  background-color: rgba($color, .8);

  &.out {
    background-color: rgba($color, 0);
  }
}