.hero-banner::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.5); /* dark overlay */
  z-index: 1;
}

.hero-banner .container {
  position: relative;
  z-index: 2;
}