:root {
  --bg: #050508;
  --bg-elevated: #0c0c10;
  --text: rgba(255, 255, 255, 0.92);
  --text-muted: rgba(255, 255, 255, 0.45);
  --accent: #7c8cff;
  --accent-soft: rgba(124, 140, 255, 0.15);
  --radius: 20px;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

/* 与 GSAP ScrollTrigger / pin 同时用时，原生 smooth 易导致滚动位置与 scrub 不同步（桌面端更明显） */
html {
  scroll-behavior: auto;
  /* 隐藏系统滚动条（Firefox / IE） */
  scrollbar-width: none;
  -ms-overflow-style: none;
}

html::-webkit-scrollbar {
  width: 0;
  height: 0;
  display: none;
}

body::-webkit-scrollbar {
  width: 0;
  height: 0;
  display: none;
}

body {
  margin: 0;
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    sans-serif;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

/* ========== 自定义阅读进度条 ========== */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  z-index: 10040;
  pointer-events: none;
}

.scroll-progress__track {
  position: absolute;
  inset: 0;
  background: linear-gradient(
    90deg,
    rgba(255, 255, 255, 0.04) 0%,
    rgba(255, 255, 255, 0.09) 50%,
    rgba(255, 255, 255, 0.04) 100%
  );
  opacity: 0.9;
}

.scroll-progress__fill {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 0%;
  max-width: 100%;
  border-radius: 0 3px 3px 0;
  background: linear-gradient(
    90deg,
    #5b63ff 0%,
    #8b9cff 45%,
    #c4b5fd 100%
  );
  box-shadow: 0 0 24px rgba(124, 140, 255, 0.45),
    0 0 8px rgba(180, 190, 255, 0.35);
  transform-origin: left center;
  will-change: width;
}

/* ========== 开屏层（揭幕前） ========== */
.page-intro {
  position: fixed;
  inset: 0;
  z-index: 10050;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  background: radial-gradient(
      ellipse 130% 100% at 50% 0%,
      rgba(55, 65, 140, 0.45) 0%,
      transparent 55%
    ),
    radial-gradient(
      ellipse 80% 60% at 80% 100%,
      rgba(40, 90, 160, 0.2) 0%,
      transparent 50%
    ),
    linear-gradient(180deg, #0a0a12 0%, var(--bg) 55%, #020203 100%);
}

.page-intro__vignette {
  position: absolute;
  inset: 0;
  background: radial-gradient(
    ellipse 70% 55% at 50% 45%,
    transparent 0%,
    rgba(0, 0, 0, 0.55) 100%
  );
  pointer-events: none;
}

.page-intro__beam {
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 1px;
  transform: translateX(-50%);
  background: linear-gradient(
    180deg,
    transparent 0%,
    rgba(124, 140, 255, 0.15) 45%,
    rgba(124, 140, 255, 0.35) 50%,
    rgba(124, 140, 255, 0.12) 55%,
    transparent 100%
  );
  opacity: 0.85;
  animation: intro-beam-pulse 3.2s ease-in-out infinite;
}

@keyframes intro-beam-pulse {
  0%,
  100% {
    opacity: 0.45;
    filter: blur(0);
  }
  50% {
    opacity: 1;
    filter: blur(0.5px);
  }
}

.page-intro__content {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 2rem;
  max-width: 520px;
}

.page-intro__kicker {
  margin: 0;
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.35em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.5);
}

.page-intro__tagline {
  margin: 1rem 0 0;
  font-size: clamp(1.5rem, 3vw, 1.5rem);
  font-weight: 300;
  letter-spacing: 0.06em;
  color: rgba(255, 255, 255, 0.88);
}

.page-intro__line {
  width: min(200px, 50vw);
  height: 1px;
  margin: 2rem auto 0;
  transform-origin: center center;
  background: linear-gradient(
    90deg,
    transparent,
    rgba(124, 140, 255, 0.5),
    rgba(255, 255, 255, 0.35),
    rgba(124, 140, 255, 0.5),
    transparent
  );
}

.page-intro__progress {
  width: min(220px, 60vw);
  height: 2px;
  margin: 2rem auto 0;
  border-radius: 2px;
  background: rgba(255, 255, 255, 0.08);
  overflow: hidden;
}

.page-intro__progress-bar {
  display: block;
  height: 100%;
  width: 100%;
  transform: scaleX(0);
  transform-origin: left center;
  background: linear-gradient(
    90deg,
    rgba(100, 120, 255, 0.4),
    rgba(180, 190, 255, 0.95),
    rgba(124, 140, 255, 0.85)
  );
  border-radius: inherit;
}

@media (prefers-reduced-motion: reduce) {
  .page-intro__beam {
    animation: none;
    opacity: 0.6;
  }
}

.noise {
  pointer-events: none;
  position: fixed;
  inset: 0;
  z-index: 9999;
  opacity: 0.035;
  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");
  mix-blend-mode: overlay;
}

/* 鼠标跟随柔光（在噪点之上，不拦截事件；left/top 由 JS 设像素，translate 居中） */
.cursor-fx {
  position: fixed;
  left: 0;
  top: 0;
  width: min(46vw, 340px);
  height: min(46vw, 340px);
  margin: 0;
  border-radius: 50%;
  transform: translate(-50%, -50%);
  pointer-events: none;
  z-index: 10000;
  opacity: 0.85;
  background: radial-gradient(
    circle at 50% 50%,
    rgba(160, 175, 255, 0.36) 0%,
    rgba(110, 140, 255, 0.12) 36%,
    transparent 64%
  );
  mix-blend-mode: screen;
  will-change: left, top;
}

.cursor-fx::after {
  content: "";
  position: absolute;
  inset: 22%;
  border-radius: 50%;
  background: radial-gradient(
    circle,
    rgba(255, 255, 255, 0.1) 0%,
    transparent 70%
  );
}

@media (prefers-reduced-motion: reduce) {
  .cursor-fx {
    display: none !important;
  }
}

.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 2rem;
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.55);
  /* 避免 mix-blend-mode 在浅色 PDF 上反色导致「看不见/发灰」（大屏更明显） */
  background: linear-gradient(
    180deg,
    rgba(5, 5, 8, 0.92) 0%,
    rgba(5, 5, 8, 0.65) 60%,
    transparent 100%
  );
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.site-nav__brand {
  font-weight: 500;
  color: rgba(255, 255, 255, 0.7);
}

.hero {
  position: relative;
  isolation: isolate;
  /* 首屏占满视口 */
  min-height: 100vh;
  min-height: 100dvh;
  min-height: 100svh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 6rem 1.5rem 4rem;
  overflow: hidden;
}

.hero__bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  background: radial-gradient(
      ellipse 120% 80% at 50% -20%,
      rgba(90, 100, 200, 0.25),
      transparent 55%
    ),
    radial-gradient(
      ellipse 80% 50% at 100% 50%,
      rgba(50, 80, 160, 0.12),
      transparent 50%
    ),
    linear-gradient(180deg, #08080c 0%, var(--bg) 45%, #030305 100%);
  animation: hero-bg-shift 17s var(--ease-out) infinite alternate;
}

@keyframes hero-bg-shift {
  0% {
    filter: hue-rotate(0deg);
    transform: scale(1);
  }
  100% {
    filter: hue-rotate(10deg);
    transform: scale(1.015);
  }
}

/* —— 极光色团：缓慢漂移 —— */
.hero__aurora {
  position: absolute;
  inset: -15% -10%;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}

.hero__aurora-blob {
  position: absolute;
  border-radius: 50%;
  filter: blur(72px);
  opacity: 0.55;
  mix-blend-mode: screen;
  will-change: transform;
}

.hero__aurora-blob--1 {
  width: min(75vw, 720px);
  height: min(75vw, 720px);
  left: -8%;
  top: -12%;
  background: radial-gradient(
    circle at 40% 40%,
    rgba(130, 150, 255, 0.55) 0%,
    rgba(80, 100, 220, 0.2) 45%,
    transparent 70%
  );
  animation: hero-aurora-1 21s ease-in-out infinite;
}

.hero__aurora-blob--2 {
  width: min(65vw, 600px);
  height: min(65vw, 600px);
  right: -5%;
  bottom: -8%;
  background: radial-gradient(
    circle at 55% 55%,
    rgba(90, 220, 255, 0.35) 0%,
    rgba(100, 120, 255, 0.22) 50%,
    transparent 72%
  );
  animation: hero-aurora-2 24s ease-in-out infinite;
}

.hero__aurora-blob--3 {
  width: min(50vw, 480px);
  height: min(50vw, 480px);
  left: 35%;
  top: 38%;
  background: radial-gradient(
    circle at 50% 50%,
    rgba(200, 180, 255, 0.28) 0%,
    rgba(124, 140, 255, 0.12) 55%,
    transparent 70%
  );
  animation: hero-aurora-3 18s ease-in-out infinite;
}

@keyframes hero-aurora-1 {
  0%,
  100% {
    transform: translate(0, 0) scale(1);
  }
  33% {
    transform: translate(8%, 6%) scale(1.06);
  }
  66% {
    transform: translate(-4%, 10%) scale(0.96);
  }
}

@keyframes hero-aurora-2 {
  0%,
  100% {
    transform: translate(0, 0) scale(1);
  }
  50% {
    transform: translate(-10%, -8%) scale(1.08);
  }
}

@keyframes hero-aurora-3 {
  0%,
  100% {
    transform: translate(0, 0) scale(1) rotate(0deg);
  }
  40% {
    transform: translate(-12%, 4%) scale(1.12) rotate(6deg);
  }
  75% {
    transform: translate(6%, -6%) scale(0.92) rotate(-4deg);
  }
}

/* —— 流动网格纹理 —— */
.hero__mesh {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: 0.45;
  background-image: radial-gradient(
      ellipse 100% 80% at 20% 30%,
      rgba(124, 140, 255, 0.12) 0%,
      transparent 50%
    ),
    radial-gradient(
      ellipse 90% 70% at 85% 70%,
      rgba(60, 180, 255, 0.08) 0%,
      transparent 45%
    ),
    radial-gradient(
      ellipse 60% 50% at 50% 100%,
      rgba(100, 80, 200, 0.06) 0%,
      transparent 50%
    );
  background-size: 120% 120%, 130% 130%, 100% 100%;
  background-position: 0% 0%, 100% 100%, 50% 0%;
  animation: hero-mesh-flow 27s linear infinite;
  mix-blend-mode: soft-light;
}

@keyframes hero-mesh-flow {
  0% {
    background-position: 0% 0%, 100% 100%, 50% 0%;
  }
  50% {
    background-position: 100% 40%, 0% 60%, 50% 100%;
  }
  100% {
    background-position: 0% 0%, 100% 100%, 50% 0%;
  }
}

/* —— 科技透视网格 —— */
.hero__grid {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: 0.35;
  background-image: linear-gradient(
      rgba(255, 255, 255, 0.04) 1px,
      transparent 1px
    ),
    linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(
    ellipse 85% 75% at 50% 42%,
    black 0%,
    rgba(0, 0, 0, 0.45) 55%,
    transparent 78%
  );
  -webkit-mask-image: radial-gradient(
    ellipse 85% 75% at 50% 42%,
    black 0%,
    rgba(0, 0, 0, 0.45) 55%,
    transparent 78%
  );
  transform: perspective(800px) rotateX(12deg) scale(1.08);
  transform-origin: 50% 80%;
  animation: hero-grid-breathe 14s ease-in-out infinite;
}

@keyframes hero-grid-breathe {
  0%,
  100% {
    opacity: 0.32;
    transform: perspective(800px) rotateX(11deg) scale(1.06);
  }
  50% {
    opacity: 0.42;
    transform: perspective(800px) rotateX(14deg) scale(1.1);
  }
}

/* —— 漂浮光球（与原有 glow 层次不同，偏装饰） —— */
.hero__orbs {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
}

.hero__orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(48px);
  opacity: 0.35;
  mix-blend-mode: screen;
  will-change: transform;
}

.hero__orb--a {
  width: min(35vw, 280px);
  height: min(35vw, 280px);
  top: 22%;
  left: 8%;
  background: rgba(160, 175, 255, 0.5);
  animation: hero-orb-float-a 11s ease-in-out infinite;
}

.hero__orb--b {
  width: min(28vw, 220px);
  height: min(28vw, 220px);
  bottom: 18%;
  left: 42%;
  background: rgba(100, 210, 255, 0.35);
  animation: hero-orb-float-b 13s ease-in-out infinite;
}

.hero__orb--c {
  width: min(32vw, 260px);
  height: min(32vw, 260px);
  top: 48%;
  right: 6%;
  background: rgba(200, 150, 255, 0.28);
  animation: hero-orb-float-c 9s ease-in-out infinite;
}

@keyframes hero-orb-float-a {
  0%,
  100% {
    transform: translate(0, 0);
  }
  50% {
    transform: translate(12px, -18px);
  }
}

@keyframes hero-orb-float-b {
  0%,
  100% {
    transform: translate(0, 0) scale(1);
  }
  50% {
    transform: translate(-16px, 14px) scale(1.08);
  }
}

@keyframes hero-orb-float-c {
  0%,
  100% {
    transform: translate(0, 0);
  }
  40% {
    transform: translate(-10px, -22px);
  }
  70% {
    transform: translate(8px, 10px);
  }
}

/* —— 扫光（极弱，避免抢内容） —— */
.hero__shimmer {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
  opacity: 0.55;
}

.hero__shimmer::after {
  content: "";
  position: absolute;
  top: -30%;
  left: -40%;
  width: 55%;
  height: 160%;
  background: linear-gradient(
    118deg,
    transparent 35%,
    rgba(255, 255, 255, 0.07) 48%,
    rgba(200, 210, 255, 0.05) 52%,
    transparent 65%
  );
  transform: skewX(-18deg);
  animation: hero-shimmer-sweep 8s ease-in-out infinite;
}

@keyframes hero-shimmer-sweep {
  0% {
    transform: translateX(-20%) skewX(-18deg);
    opacity: 0;
  }
  15% {
    opacity: 1;
  }
  45% {
    transform: translateX(220%) skewX(-18deg);
    opacity: 0.9;
  }
  55%,
  100% {
    transform: translateX(220%) skewX(-18deg);
    opacity: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .hero__bg,
  .hero__aurora-blob,
  .hero__mesh,
  .hero__grid,
  .hero__orb,
  .hero__shimmer::after {
    animation: none !important;
  }

  .hero__mesh {
    opacity: 0.35;
  }

  .hero__grid {
    opacity: 0.28;
    transform: perspective(800px) rotateX(12deg) scale(1.06);
  }

  .hero__shimmer::after {
    opacity: 0;
  }
}

.hero__glow {
  position: absolute;
  z-index: 0;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.5;
  pointer-events: none;
}

.hero__glow--one {
  width: min(60vw, 520px);
  height: min(60vw, 520px);
  top: 15%;
  left: 50%;
  transform: translateX(-50%);
  background: radial-gradient(
    circle,
    rgba(124, 140, 255, 0.35) 0%,
    transparent 70%
  );
}

.hero__glow--two {
  width: min(40vw, 360px);
  height: min(40vw, 360px);
  bottom: 10%;
  right: 5%;
  background: radial-gradient(
    circle,
    rgba(100, 200, 255, 0.2) 0%,
    transparent 70%
  );
}

.hero__inner {
  position: relative;
  z-index: 2;
  max-width: 920px;
  text-align: center;
}

.hero__eyebrow {
  margin: 0 0 1rem;
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.hero__title {
  margin: 0;
  font-size: clamp(2.5rem, 8vw, 4.75rem);
  font-weight: 300;
  letter-spacing: -0.03em;
  line-height: 1.05;
  background: linear-gradient(
    115deg,
    #ffffff 0%,
    rgba(245, 246, 255, 0.95) 38%,
    rgba(190, 200, 255, 0.92) 72%,
    rgba(160, 175, 255, 0.88) 100%
  );
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero__subtitle {
  margin: 1.5rem 0 0;
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  font-weight: 400;
  color: var(--text-muted);
  letter-spacing: 0.02em;
  line-height: 1.6;
}

.hero__cta {
  margin-top: 3.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  color: var(--text-muted);
  font-size: 0.75rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

.hero__scroll-line {
  width: 1px;
  height: 48px;
  background: linear-gradient(
    180deg,
    rgba(255, 255, 255, 0.4),
    rgba(255, 255, 255, 0)
  );
}

.story {
  position: relative;
  z-index: 1;
}

.story-section {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  padding: 3rem 1.5rem 4rem;
  padding-top: max(3rem, env(safe-area-inset-top, 0px));
  gap: 1.25rem;
}

.story-section__label {
  margin: 0;
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.story-section__frame {
  width: 100%;
  max-width: min(1120px, 100%);
  /* 不要用 overflow:hidden：配合图片 transform 视差会裁掉上下边缘 */
  overflow: visible;
  background: var(--bg-elevated);
  border-radius: var(--radius);
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.06),
    0 40px 120px -40px rgba(0, 0, 0, 0.85);
}

.story-section__frame img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  vertical-align: middle;
  /* 保证整页缩放在容器内完整可见 */
  object-fit: contain;
  object-position: top center;
  -webkit-user-drag: none;
  user-drag: none;
  -webkit-user-select: none;
  user-select: none;
}

/* 第 12 页：PDF 上叠两个可点视频（位置用相对画框的 %，与图同比例缩放，手机与桌面对齐方式一致） */
.story-section__frame--with-videos {
  position: relative;
}

.story-page12-videos {
  position: absolute;
  inset: 0;
  pointer-events: none;
  border-radius: var(--radius);
}

.story-page12-slot {
  position: absolute;
  pointer-events: auto;
  /* 宽度相对 .story-section__frame 内容盒，与底图同宽缩放 */
  width: min(44%, 600px);
  max-width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.45),
    0 0 0 1px rgba(255, 255, 255, 0.12);
  background: #0a0a10;
}

/* 右上第一个（与桌面同一套百分比，勿在窄屏另改 top/right，否则与 PDF 错位） */
.story-page12-slot--a {
  top: 8.5%;
  right: max(3%, env(safe-area-inset-right, 0px));
}

/* 下方第二个 */
.story-page12-slot--b {
  top: 52%;
  right: max(3%, env(safe-area-inset-right, 0px));
}

.story-page12-video {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
  vertical-align: middle;
  cursor: pointer;
}

.story-page12-play {
  position: absolute;
  inset: 0;
  margin: auto;
  width: 3.25rem;
  height: 3.25rem;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 0;
  color: transparent;
  background: rgba(5, 5, 12, 0.55);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.2);
  transition: transform 0.2s var(--ease-out), background 0.2s;
}

.story-page12-play::after {
  content: "";
  position: absolute;
  left: 54%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 0.55rem 0 0.55rem 0.95rem;
  border-color: transparent transparent transparent rgba(255, 255, 255, 0.95);
}

.story-page12-play:hover {
  transform: scale(1.06);
  background: rgba(90, 100, 200, 0.45);
}

.story-page12-play[hidden] {
  display: none;
}

@media (max-width: 640px) {
  /* 不重写 top/right/width，避免与 PDF 对不齐；只加强触控与刘海侧安全区 */
  .story-page12-play {
    width: max(3.25rem, 44px);
    height: max(3.25rem, 44px);
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
  }

  .story-page12-video {
    touch-action: manipulation;
  }

  .story-section__frame--with-videos {
    /* 避免窄屏圆角裁切热区时的视觉误差 */
    -webkit-touch-callout: none;
  }
}

.back-to-top {
  position: fixed;
  left: max(1rem, env(safe-area-inset-left, 0px));
  bottom: max(1.25rem, env(safe-area-inset-bottom, 0px));
  z-index: 10035;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  padding: 0;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  color: rgba(255, 255, 255, 0.88);
  background: linear-gradient(
    145deg,
    rgba(28, 30, 45, 0.92) 0%,
    rgba(12, 14, 24, 0.96) 100%
  );
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.1),
    0 12px 40px -12px rgba(0, 0, 0, 0.65);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.28s var(--ease-out), transform 0.28s var(--ease-out),
    visibility 0.28s;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.back-to-top--visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  color: #fff;
  box-shadow: 0 0 0 1px rgba(124, 140, 255, 0.35),
    0 14px 44px -10px rgba(60, 80, 180, 0.35);
}

.back-to-top:active {
  transform: translateY(1px) scale(0.98);
}

.back-to-top--visible:active {
  transform: translateY(1px) scale(0.98);
}

.back-to-top__icon {
  display: block;
  margin-top: -2px;
}

@media (prefers-reduced-motion: reduce) {
  .back-to-top {
    transition: opacity 0.2s ease, visibility 0.2s;
  }
}

.footer {
  padding: 4rem 1.5rem;
  text-align: center;
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.08em;
}

@media (min-width: 1024px) {
  .story-section {
    padding: 5.5rem 3rem 5rem;
  }

  /* 大屏：画框略放宽，避免 max-width 过小导致「只占中间一条」的观感 */
  .story-section__frame {
    max-width: min(1400px, 100%);
  }
}

@media (max-width: 640px) {
  .site-nav {
    padding: 1rem 1.25rem;
  }

  .hero__title {
    font-size: clamp(2rem, 10vw, 2.75rem);
  }
}