.hero {
  position: relative;
}

.hero .overlay {
  position: absolute;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.5);
  top: 0;
  left: 0;
  z-index: 1;
}

.hero .single-slide {
  position: relative;
  z-index: 2;
}

.hero-slider {
  position: absolute;
  z-index: 0;
}