#img-cover{
  position: relative;
}
#img-cover::before{
  content: '';
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
  background-color: rgba(0, 0, 0, .4);
  z-index: 2;
}