Sticky Header with Shadow

.sticky-header {
  position: sticky;
  top: 0;
  background: rgba(13, 17, 38, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 16px 24px;
  z-index: 100;
  transition: box-shadow 0.3s ease;
}

.sticky-header.scrolled {
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

/* Alternative: Pure CSS shadow on scroll */
.sticky-header-auto {
  position: sticky;
  top: -1px;
  padding-top: calc(16px + 1px);
  background: #0d1126;
  z-index: 100;
}

.sticky-header-auto::before {
  content: '';
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  height: 20px;
  background: linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0.2),
    transparent
  );
  opacity: 0;
  transition: opacity 0.3s;
  pointer-events: none;
}

.sticky-header-auto.stuck::before {
  opacity: 1;
}