//
// Overlay
//
// @param  hex  hex
// @param  int  opacity
//
_overlay(hex, opacity = 1) {
  position: relative;

  &::before {
    _position(absolute, 0, 0, 0, 0);
    content: '';

    if (1 == opacity) {
      background-color: hex;
    } else {
      background-color: rgba(hex, opacity);
    }
  }
}