/* ヒーローの動くグラデーション背景。handoff/gradient-background の指示書を元に、scrolltide.co を参考にして動きを強めた版
   （光の帯の揺れ、粒子のきらめき、フィルムの粒子感、マウスとスクロールへの反応を追加）。色はページ側の CSS 変数で上書きする */

.gradient-bg {
  --gbg-base: #ffffff;
  --gbg-deep: #0d40cc;
  --gbg-azure: #1f85fa;
  --gbg-cyan: #1accf2;
  --gbg-mint: #6bf2d1;

  position: relative;
  overflow: hidden;
  min-height: 100vh;
  min-height: 100svh;
  display: flex;
  align-items: center;
  background: var(--gbg-base);
  isolation: isolate;
}

.gradient-bg__fallback {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(55% 70% at 80% 45%, color-mix(in srgb, var(--gbg-azure) 30%, var(--gbg-base)) 0%, transparent 70%),
    radial-gradient(40% 50% at 92% 85%, color-mix(in srgb, var(--gbg-mint) 40%, var(--gbg-base)) 0%, transparent 70%),
    var(--gbg-base);
}

.gradient-bg[data-fade="right"] .gradient-bg__fallback {
  background:
    radial-gradient(55% 70% at 20% 45%, color-mix(in srgb, var(--gbg-azure) 30%, var(--gbg-base)) 0%, transparent 70%),
    radial-gradient(40% 50% at 8% 85%, color-mix(in srgb, var(--gbg-mint) 40%, var(--gbg-base)) 0%, transparent 70%),
    var(--gbg-base);
}

.gradient-bg__canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.gradient-bg__grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(30, 58, 95, 0.07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(30, 58, 95, 0.07) 1px, transparent 1px);
  background-size: 56px 56px;
  -webkit-mask-image: linear-gradient(90deg, transparent 0%, transparent 35%, #000 70%);
  mask-image: linear-gradient(90deg, transparent 0%, transparent 35%, #000 70%);
  pointer-events: none;
}

.gradient-bg[data-fade="right"] .gradient-bg__grid {
  -webkit-mask-image: linear-gradient(270deg, transparent 0%, transparent 35%, #000 70%);
  mask-image: linear-gradient(270deg, transparent 0%, transparent 35%, #000 70%);
}

.gradient-bg[data-fade="none"] .gradient-bg__grid {
  -webkit-mask-image: none;
  mask-image: none;
}

.gradient-bg[data-fade="none"] .gradient-bg__grain {
  -webkit-mask-image: none;
  mask-image: none;
}

.gradient-bg__geo {
  position: absolute;
  right: -6vw;
  top: 50%;
  width: min(62vw, 820px);
  aspect-ratio: 1;
  transform: translate(calc(var(--gbg-mx, 0) * -18px), calc(-50% + var(--gbg-my, 0) * 14px));
  pointer-events: none;
  opacity: 0.9;
}

.gradient-bg[data-fade="right"] .gradient-bg__geo {
  right: auto;
  left: -6vw;
}

.gradient-bg__geo .gbg-spin {
  transform-origin: 50% 50%;
  animation: gbg-spin 90s linear infinite;
}

.gradient-bg__geo .gbg-spin-rev {
  transform-origin: 50% 50%;
  animation: gbg-spin 140s linear infinite reverse;
}

@keyframes gbg-spin {
  to {
    transform: rotate(360deg);
  }
}

.gradient-bg__grain {
  position: absolute;
  inset: -50%;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' stitchTiles='stitch'/%3E%3CfeColorMatrix values='0 0 0 0 0.5 0 0 0 0 0.5 0 0 0 0 0.5 0 0 0 1.4 -0.2'/%3E%3C/filter%3E%3Crect width='160' height='160' filter='url(%23n)'/%3E%3C/svg%3E");
  opacity: 0.12;
  mix-blend-mode: overlay;
  -webkit-mask-image: linear-gradient(90deg, transparent 0%, transparent 30%, #000 65%);
  mask-image: linear-gradient(90deg, transparent 0%, transparent 30%, #000 65%);
  animation: gbg-grain 2s steps(4) infinite;
  pointer-events: none;
}

@keyframes gbg-grain {
  0% { transform: translate(0, 0); }
  25% { transform: translate(-3%, 2%); }
  50% { transform: translate(2%, -3%); }
  75% { transform: translate(-2%, -1%); }
  100% { transform: translate(0, 0); }
}

.gradient-bg__content {
  position: relative;
  z-index: 1;
  width: 100%;
}

@media (max-width: 767px) {
  .gradient-bg__geo {
    right: -40vw;
    top: 30%;
    width: 110vw;
    opacity: 0.55;
  }

  .gradient-bg[data-fade="right"] .gradient-bg__geo {
    right: auto;
    left: -40vw;
  }

  .gradient-bg .gradient-bg__grid,
  .gradient-bg[data-fade="right"] .gradient-bg__grid,
  .gradient-bg .gradient-bg__grain {
    -webkit-mask-image: linear-gradient(180deg, transparent 0%, #000 100%);
    mask-image: linear-gradient(180deg, transparent 0%, #000 100%);
  }
}

@media (prefers-reduced-motion: reduce) {

  .gradient-bg__geo .gbg-spin,
  .gradient-bg__geo .gbg-spin-rev,
  .gradient-bg__grain {
    animation: none;
  }
}