.details-container::before {
  content: "";
  position: absolute;
  top: 0; /* can delete top/left etc if sizes are 100% */
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(255, 255, 255, 0.5);
  z-index: -1; /* must be lower number than objects needing to be in front */
}