/* ============================================
   BACKGROUND CONTAINER (plain holder divs)
   ============================================ */
.background-container {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    z-index: 0;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}

/* ============================================
   CLOUD OVERLAY LAYERS (displacement swirl)
   mix-blend-mode: screen on dark body → rainbow glow
   z-index 1: sits above background containers, below content
   ============================================ */
.cloud-layer {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    pointer-events: none;
    mix-blend-mode: screen;
    z-index: 1;
    will-change: transform;
    -webkit-mask-image: linear-gradient(to bottom,
        transparent 3%, black 18%, black 82%, transparent 97%);
    mask-image: linear-gradient(to bottom,
        transparent 3%, black 18%, black 82%, transparent 97%);
}

.cloud-inner {
    position: absolute;
    inset: 0;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}
.cloud-inner:first-child { z-index: 1; opacity: 1; }
.cloud-inner:last-child  { z-index: 2; opacity: 0; }

.cloud-layer-1 {
    filter: url(#cloud-warp);
    animation: cloud-drift-1 20s ease-in-out infinite,
               cloud-fade    26s ease-in-out infinite;
}

.cloud-layer-2 {
    filter: url(#cloud-warp-b);
    animation: cloud-drift-2 24s ease-in-out infinite,
               cloud-fade    26s -3s ease-in-out infinite;
}

@keyframes cloud-drift-1 {
    0%, 100% { transform: scale(1.10) translate(-1.0%, -0.5%) rotate(-3deg); }
    25%      { transform: scale(1.07) translate( 0.7%,  0.8%) rotate( 1deg); }
    55%      { transform: scale(1.06) translate( 0.9%,  0.4%) rotate( 4deg); }
    78%      { transform: scale(1.08) translate(-0.4%,  0.6%) rotate(-1deg); }
}

@keyframes cloud-drift-2 {
    0%, 100% { transform: scale(1.08) translate( 0.7%, -0.5%) rotate( 3deg); }
    30%      { transform: scale(1.10) translate(-0.5%,  0.5%) rotate(-2deg); }
    62%      { transform: scale(1.07) translate(-0.9%,  0.9%) rotate(-4deg); }
}

@keyframes cloud-fade {
    0%, 100% { opacity: 0.96; }
    32%      { opacity: 0.96; }
    50%      { opacity: 0.42; }
    68%      { opacity: 0.96; }
}

/* Phones: only pages that opt in (index.html) show the animation; others keep their own still-image fallback */
@media (max-width: 768px) {
    html:not(.bg-phone-anim) .cloud-layer { display: none; }
}

/* Crossfade fallback: reduced motion or a struggling device (set by js/bg-anim.js) */
.bg-fade .cloud-layer {
    filter: none !important;
    animation: none !important;
    transform: scale(1.08);
}
/* Phones/tablets: one plain layer — no blending, mask or extra GPU layer to recomposite while scrolling */
@media (max-width: 768px), (pointer: coarse) {
    .bg-fade .cloud-layer { mix-blend-mode: normal; -webkit-mask-image: none; mask-image: none; will-change: auto; }
    .bg-fade .cloud-layer-2 { display: none; }
}