/**
 * Forge ambient — section background atmosphere (narrative SVG layer).
 * Separate from component motion (.pulse, .breathe) and ks-living-*.
 * Compose: .forge-ambient-bg.ks-ambient-bg[data-ks-bg-src="..."] + ks-animated-backgrounds.js
 */
.forge-ambient {
  position: relative;
  overflow: hidden;
  isolation: isolate;
}

.forge-ambient-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: var(--forge-ambient-opacity, 0.52);
}

.forge-ambient-bg > svg {
  width: 100%;
  height: 100%;
  display: block;
  transform: scale(var(--forge-ambient-scale, 1));
  transform-origin: center center;
  filter: blur(var(--forge-ambient-blur, 0px));
}

.forge-ambient-scrim {
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background: var(--forge-ambient-scrim, transparent);
}

.forge-ambient-content {
  position: relative;
  z-index: 2;
}

/* Intensity */
.forge-ambient--subtle {
  --forge-ambient-opacity: 0.34;
  --forge-ambient-node-opacity: 0.28;
  --forge-ambient-spark-opacity: 0.55;
  --forge-ambient-scrim: color-mix(in srgb, var(--forge-bg) 38%, transparent);
}

.forge-ambient--medium {
  --forge-ambient-opacity: 0.52;
  --forge-ambient-node-opacity: 0.42;
  --forge-ambient-spark-opacity: 0.82;
}

.forge-ambient--hero {
  --forge-ambient-opacity: 0.62;
  --forge-ambient-node-opacity: 0.52;
  --forge-ambient-spark-opacity: 0.95;
  --forge-ambient-scrim: color-mix(in srgb, var(--forge-bg) 24%, transparent);
}

/* Motion speed (CSS-driven parts; SMIL uses long fixed durs — still modifier handled in JS) */
.forge-ambient--slow {
  --forge-ambient-speed: 1.35;
}

.forge-ambient--expressive {
  --forge-ambient-speed: 0.72;
}

.forge-ambient--still {
  --forge-ambient-speed: 0;
}

/* Theme context helpers */
.forge-ambient--on-dark {
  --forge-ambient-line: color-mix(in srgb, var(--forge-cyan) 16%, transparent);
  --forge-ambient-line-soft: color-mix(in srgb, var(--forge-text-3) 26%, transparent);
}

.forge-ambient--on-light {
  --forge-ambient-line: color-mix(in srgb, var(--forge-cyan) 24%, transparent);
  --forge-ambient-line-soft: color-mix(in srgb, var(--forge-text-3) 48%, transparent);
}

/* Per-style SVG hooks (opacity / accents; keep SVGs token-driven) */
.forge-ambient--aurora-flow .forge-ambient-bg svg .fa-aurora-glow {
  opacity: 0.55;
}

.forge-ambient--signal-river .forge-ambient-bg svg .fa-river-back {
  opacity: 0.65;
}

.forge-ambient--mesh-bloom .forge-ambient-bg svg .fa-mesh-node {
  opacity: var(--forge-ambient-node-opacity, 0.42);
}

.forge-ambient--mesh-bloom .forge-ambient-bg svg .fa-mesh-spark {
  opacity: var(--forge-ambient-spark-opacity, 0.82);
}

.forge-ambient--contour-drift .forge-ambient-bg svg path {
  vector-effect: non-scaling-stroke;
}

.forge-ambient--orbit-field .forge-ambient-bg svg .fa-orbit-hub {
  opacity: var(--forge-ambient-node-opacity, 0.5);
}

.forge-ambient--constellation-sweep .forge-ambient-bg svg .fa-const-edge {
  opacity: 0.4;
}

@keyframes fa-shimmer-x {
  0% {
    opacity: 0.35;
  }
  50% {
    opacity: 0.7;
  }
  100% {
    opacity: 0.35;
  }
}

.forge-ambient:not(.forge-ambient--still) .forge-ambient-bg svg .fa-css-shimmer {
  animation: fa-shimmer-x calc(14s * var(--forge-ambient-speed, 1)) ease-in-out infinite;
}

@media (prefers-reduced-motion: reduce) {
  .forge-ambient-bg svg .fa-css-shimmer {
    animation: none !important;
  }

  .forge-ambient {
    --forge-ambient-blur: 0px;
  }
}