#zen-background {
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 100%;
}
#zen-background img {
  width: 100%;
  height: 100%;
}
#zen-background-overlay {
  background: rgba(0,0,0,0.6);
  position: absolute;
  z-index: 2;
  width: 100%;
  height: 100%;
}