/* =========================================================
   首页开场：暗场体积光 + 浮尘（实时生成，无素材）
   仅 index.html 引入
   ========================================================= */

.intro {
  --hdr: 68px;
  position: relative;
  height: 180vh;
  background: transparent; /* 背景交给 Grainient 着色器 */
}
.intro__stage {
  position: sticky;
  top: var(--hdr);
  height: calc(100vh - var(--hdr));
  overflow: hidden;
  display: grid;
  place-items: center;
  background: transparent;
}

/* 画布与质感层 */
.intro__canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
.intro__scans,
.intro__grain,
.intro__vignette { position: absolute; inset: 0; pointer-events: none; }
.intro__scans {
  z-index: 4;
  opacity: 0.3;
  mix-blend-mode: screen;
  background: repeating-linear-gradient(
    180deg,
    rgba(150, 225, 255, 0.035) 0 1px,
    transparent 1px 4px
  );
}
.intro__grain {
  z-index: 5;
  inset: -50%;
  opacity: 0.05;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='160' height='160'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3'/></filter><rect width='160' height='160' filter='url(%23n)'/></svg>");
  animation: introGrain 1.1s steps(3) infinite;
}
@keyframes introGrain {
  0% { transform: translate3d(0, 0, 0); }
  33% { transform: translate3d(-2%, 1%, 0); }
  66% { transform: translate3d(1%, -2%, 0); }
  100% { transform: translate3d(0, 0, 0); }
}
.intro__vignette {
  z-index: 5;
  background: radial-gradient(
    115% 100% at 50% 45%,
    transparent 38%,
    rgba(0, 0, 0, 0.86) 100%
  );
}

/* 文案 */
/* 三段式：顶部小字 / 中间大标题 / 底部说明与按钮 */
.intro__content {
  position: relative;
  z-index: 6;
  width: 100%;
  max-width: 1100px;
  height: 100%;
  margin: 0 auto;
  padding: 4vh var(--gut) 4vh;
  display: grid;
  grid-template-rows: auto 1fr auto;
  justify-items: center;
  text-align: center;
  will-change: transform;
}
.intro__eyebrow { align-self: start; }
.intro__title { align-self: center; }
.intro__bottom {
  align-self: end;
  display: grid;
  justify-items: center;
  gap: clamp(14px, 2.2vw, 22px);
  padding-bottom: 5vh;
}
.intro__eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin: 0 0 clamp(18px, 2.4vw, 28px);
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.24em;
  color: rgba(163, 224, 255, 0.82);
}
.intro__eyebrow::before {
  content: "";
  width: 26px;
  height: 1px;
  background: var(--accent);
  opacity: 0.7;
}
.intro__title {
  margin: 0;
  font-size: clamp(32px, 5.6vw, 82px);
  line-height: 1.14;
  font-weight: 600;
  letter-spacing: var(--track, 0.09em);
  color: #f2f9ff;
  text-shadow: 0 0 60px rgba(0, 140, 255, 0.3);
}
.intro__title span {
  color: #8fd8ff;
  text-shadow: 0 0 40px rgba(143, 216, 255, 0.45);
}
.intro__lead {
  margin: clamp(18px, 2.6vw, 30px) auto 0;
  max-width: 46ch;
  font-size: clamp(14px, 1.2vw, 16.5px);
  line-height: 1.95;
  color: #b9cbdb;
}
.intro__actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 14px;
  margin: 0;
}
.intro__actions .btn--ghost { border-color: rgba(255, 255, 255, 0.22); }

/* 底部指示与进度 */
.intro__foot {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 6;
  padding: 0 var(--gut) 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.22em;
  color: rgba(120, 175, 200, 0.55);
  pointer-events: none;
}
.intro__bar {
  position: absolute;
  left: var(--gut);
  right: var(--gut);
  bottom: 12px;
  height: 1px;
  background: rgba(150, 225, 255, 0.12);
}
.intro__bar i {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, rgba(60, 120, 255, 0.6), #8fd8ff);
  box-shadow: 0 0 8px rgba(143, 216, 255, 0.55);
}
.intro__skip {
  position: absolute;
  right: var(--gut);
  top: 14px;
  z-index: 7;
  pointer-events: auto;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  color: rgba(140, 190, 210, 0.62);
  text-decoration: none;
  border-bottom: 1px solid rgba(143, 216, 255, 0.22);
  padding-bottom: 2px;
}
.intro__skip:hover { color: #8fd8ff; }
.intro__hint {
  position: static;
  margin: 4px 0 0;
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.3em;
  color: rgba(140, 190, 210, 0.6);
  opacity: var(--hint, 1);
  pointer-events: none;
}

@media (max-width: 900px) {
  .intro { height: 150vh; --hdr: 60px; }
  .intro__lead { max-width: 34ch; }
  .intro__hint { display: none; }
  .intro__eyebrow {
    flex-wrap: wrap;
    justify-content: center;
    font-size: 9.5px;
    letter-spacing: 0.18em;
    line-height: 2;
    padding: 0 6px;
  }
  .intro__eyebrow::before { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .intro__grain { animation: none; }
  .intro { height: 100vh; }
  .intro__stage { position: relative; }
  .intro__bar { display: none; }
}




/* 标题逐字显现（ScrollReveal 效果的移植） */
.intro__title.is-split { transform-origin: 50% 50%; }
.intro__title .w {
  display: inline-block;
  will-change: opacity, filter;
}
@media (prefers-reduced-motion: reduce) {
  .intro__title .w { opacity: 1 !important; filter: none !important; }
}