#black-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1001;
  background: #000;
  background: rgba(0,0,0,0.6);
  overflow: hidden;
  display: none;
}

body.show-black-overlay #black-overlay {
  display: block;
}
  
.overlay-trigger {
  position: relative;
  z-index: 1002;
}