/* ── Background Layers ──────────────────────────── */

/* Layer 1: Frame Slideshow */
.bg-slideshow {
  position: fixed;
  inset: 0;
  z-index: 0;
  overflow: hidden;
}

.bg-slideshow__frame {
  position: absolute;
  inset: -20px;
  background-size: cover;
  background-position: center;
  opacity: 0;
  transform: scale(1);
  will-change: opacity, transform;
}

.bg-slideshow__frame.active {
  opacity: 1;
}

.bg-slideshow__frame.zooming {
  transform: scale(var(--zoom-amount));
}

/* Layer 2: Color Overlay */
.bg-overlay {
  position: fixed;
  inset: 0;
  z-index: 1;
  background: var(--overlay-color);
  mix-blend-mode: var(--overlay-blend);
  pointer-events: none;
}

/* Layer 2b: Texture Overlay */
.bg-texture {
  position: fixed;
  inset: 0;
  z-index: 1;
  background-image: url('../../texture.jpg');
  background-size: cover;
  background-position: center;
  opacity: 0.12;
  mix-blend-mode: screen;
  pointer-events: none;
}

/* Layer 3: Scan Lines */
.bg-scanlines {
  position: fixed;
  inset: 0;
  z-index: 2;
  background: repeating-linear-gradient(
    0deg,
    transparent,
    transparent 2px,
    rgba(0, 0, 0, var(--scanline-opacity)) 2px,
    rgba(0, 0, 0, var(--scanline-opacity)) 4px
  );
  pointer-events: none;
}

/* Layer 4: Film Grain */
.bg-grain {
  position: fixed;
  inset: -50%;
  width: 200%;
  height: 200%;
  z-index: 3;
  opacity: var(--grain-opacity);
  pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  background-size: 256px 256px;
  animation: grainDrift 0.5s steps(4) infinite;
}

@keyframes grainDrift {
  0%   { transform: translate(0, 0); }
  25%  { transform: translate(-5%, -5%); }
  50%  { transform: translate(3%, -8%); }
  75%  { transform: translate(-8%, 3%); }
  100% { transform: translate(5%, 5%); }
}

/* Layer 5: Vignette */
.bg-vignette {
  position: fixed;
  inset: 0;
  z-index: 4;
  background: radial-gradient(
    ellipse at center,
    transparent 40%,
    rgba(16, 19, 35, 0.6) 100%
  );
  pointer-events: none;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  .bg-slideshow__frame {
    animation: none !important;
  }
  .bg-slideshow__frame:first-child {
    opacity: 1 !important;
  }
  .bg-grain {
    animation: none !important;
  }
}