/* =========================================================
   中欧体育KOK 全站共享样式 /assets/site.css
   ========================================================= */

/* ---------- 1. 变量与重置 ---------- */
:root {
  --color-primary: #0B1D3A;
  --color-primary-light: #1E3A5F;
  --color-gold: #D4AF37;
  --color-gold-light: #F0C75E;
  --color-red: #D62828;
  --color-red-light: #EF5350;
  --color-cloud: #F5F7FA;
  --color-ink: #2D3748;
  --color-gray: #718096;
  --color-white: #FFFFFF;

  --font-display: 'Anton', 'Impact', 'Arial Black', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-body: 'Roboto', 'Open Sans', 'Helvetica Neue', 'PingFang SC', 'Microsoft YaHei', Arial, sans-serif;

  --container-max: 1280px;
  --radius-pill: 999px;
  --radius-lg: 18px;
  --radius-md: 12px;
  --shadow-float: 0 12px 32px rgba(11, 29, 58, 0.28);
  --shadow-card: 0 6px 24px rgba(11, 29, 58, 0.08);
  --transition-fast: 0.2s ease;
  --transition-base: 0.3s ease;
}

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

html {
  line-height: 1.5;
  text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-ink);
  background-color: var(--color-cloud);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  line-height: 1.2;
  margin: 0 0 0.5em;
  color: var(--color-primary);
}

p { margin: 0 0 1em; }
img, svg, video { max-width: 100%; height: auto; display: block; }
ul, ol { margin: 0; padding: 0; }
button { font-family: inherit; }

::selection {
  background: rgba(212, 175, 55, 0.35);
  color: var(--color-primary);
}

:focus-visible {
  outline: 3px solid var(--color-gold-light);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------- 2. 布局工具 ---------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: 24px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- 3. 章节 ---------- */
.section { padding-block: 72px; }

.section--dark {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
  color: var(--color-cloud);
}

.section--dark h1,
.section--dark h2,
.section--dark h3,
.section--dark h4,
.section--dark h5,
.section--dark h6 { color: var(--color-cloud); }

.section-head { max-width: 760px; margin-bottom: 36px; }

.section-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-gold);
  margin-bottom: 10px;
}

.section-eyebrow::before {
  content: '';
  width: 24px;
  height: 2px;
  background: var(--color-gold);
  flex: none;
}

.section-title {
  font-size: clamp(26px, 3.6vw, 44px);
  text-transform: uppercase;
  letter-spacing: 0.01em;
}

.section-subtitle {
  font-size: 16px;
  color: var(--color-gray);
  max-width: 640px;
}

.section--dark .section-subtitle { color: rgba(245, 247, 250, 0.7); }

/* ---------- 4. 面包屑 ---------- */
.breadcrumbs { padding: 14px 0 4px; }

.breadcrumbs ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 4px;
  font-size: 14px;
  color: var(--color-gray);
}

.breadcrumbs li { display: flex; align-items: center; }
.breadcrumbs li + li::before {
  content: '/';
  color: rgba(212, 175, 55, 0.7);
  margin-inline: 6px;
}

.breadcrumbs a {
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
}

.breadcrumbs a:hover { color: var(--color-gold); }
.breadcrumbs__current { color: var(--color-gray); }

/* ---------- 5. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 13px 26px;
  border: none;
  border-radius: var(--radius-pill);
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-decoration: none;
  cursor: pointer;
  transition:
    background var(--transition-base),
    color var(--transition-base),
    box-shadow var(--transition-base),
    transform var(--transition-base);
}

.btn--gold {
  background: linear-gradient(135deg, var(--color-gold) 0%, var(--color-gold-light) 100%);
  color: var(--color-primary);
  box-shadow: 0 6px 18px rgba(212, 175, 55, 0.35);
}

.btn--gold:hover {
  box-shadow: 0 10px 26px rgba(212, 175, 55, 0.5);
  transform: translateY(-2px);
}

.btn--outline {
  background: transparent;
  color: var(--color-gold);
  border: 1px solid rgba(212, 175, 55, 0.7);
}

.btn--outline:hover { background: rgba(212, 175, 55, 0.12); }

.btn--red {
  background: linear-gradient(135deg, var(--color-red) 0%, var(--color-red-light) 100%);
  color: var(--color-white);
  box-shadow: 0 6px 18px rgba(214, 40, 40, 0.28);
}

.btn--red:hover {
  box-shadow: 0 10px 26px rgba(214, 40, 40, 0.4);
  transform: translateY(-2px);
}

/* ---------- 6. 标签 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 14px;
  border-radius: var(--radius-pill);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.06em;
  line-height: 1.4;
  border: 1px solid transparent;
  background: var(--color-primary-light);
  color: var(--color-cloud);
}

.tag::before {
  content: '';
  width: 6px;
  height: 6px;
  transform: rotate(45deg);
  background: currentColor;
  flex: none;
}

.tag--gold {
  background: rgba(212, 175, 55, 0.14);
  border-color: rgba(212, 175, 55, 0.45);
  color: var(--color-gold);
}

.tag--red {
  background: rgba(214, 40, 40, 0.12);
  border-color: rgba(214, 40, 40, 0.35);
  color: var(--color-red-light);
}

/* ---------- 7. 卡片与研究面板 ---------- */
.card {
  background: var(--color-white);
  border: 1px solid #e4e8ef;
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-card);
  transition:
    transform var(--transition-base),
    box-shadow var(--transition-base),
    border-color var(--transition-base);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 14px 34px rgba(11, 29, 58, 0.14);
  border-color: rgba(212, 175, 55, 0.45);
}

.card--dark {
  background: linear-gradient(140deg, var(--color-primary) 0%, #14294a 60%, var(--color-primary-light) 100%);
  color: var(--color-cloud);
  border-color: transparent;
}

.card--dark h3,
.card--dark h4 { color: var(--color-cloud); }

.print-frame {
  position: relative;
  background: var(--color-white);
  border: 1px dashed rgba(212, 175, 55, 0.55);
  border-radius: var(--radius-md);
  padding: 26px;
}

.print-frame::before {
  content: '';
  position: absolute;
  top: 10px;
  right: 10px;
  width: 14px;
  height: 14px;
  border-top: 2px solid var(--color-red);
  border-right: 2px solid var(--color-red);
  border-radius: 0 4px 0 0;
}

.print-frame::after {
  content: '';
  position: absolute;
  bottom: 10px;
  left: 10px;
  width: 14px;
  height: 14px;
  border-bottom: 2px solid var(--color-gold);
  border-left: 2px solid var(--color-gold);
  border-radius: 0 0 0 4px;
}

/* ---------- 8. 网格 ---------- */
.grid-2,
.grid-3,
.grid-4 {
  display: grid;
  gap: 24px;
}

@media (min-width: 768px) {
  .grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (min-width: 992px) {
  .grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}

@media (min-width: 1200px) {
  .grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* ---------- 9. 媒体与数据可视化框架 ---------- */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  border-radius: var(--radius-lg);
  border: 1px solid rgba(212, 175, 55, 0.28);
  background:
    radial-gradient(circle at 72% 24%, rgba(212, 175, 55, 0.2) 0%, transparent 42%),
    linear-gradient(140deg, var(--color-primary-light) 0%, var(--color-primary) 100%);
  box-shadow: var(--shadow-card);
}

.media-frame::before {
  content: '';
  position: absolute;
  inset: 0;
  z-index: 2;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(245, 247, 250, 0.055) 1px, transparent 1px),
    linear-gradient(90deg, rgba(245, 247, 250, 0.055) 1px, transparent 1px);
  background-size: 26px 26px;
}

.media-frame > * { position: relative; z-index: 1; }

.media-frame img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 3 / 4; }
.media-frame--square { aspect-ratio: 1; }

.media-frame__note {
  position: absolute;
  left: 14px;
  bottom: 14px;
  z-index: 3;
  display: inline-block;
  padding: 4px 14px;
  margin: 0;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.05em;
  color: var(--color-gold-light);
  background: rgba(11, 29, 58, 0.82);
  border: 1px solid rgba(212, 175, 55, 0.4);
  border-radius: var(--radius-pill);
  line-height: 1.5;
}

.media-frame__note::before {
  content: '';
  display: inline-block;
  width: 6px;
  height: 6px;
  margin-right: 8px;
  background: var(--color-gold-light);
  transform: rotate(45deg);
}

/* ---------- 10. 数据表格 ---------- */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  background: var(--color-white);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.data-table th,
.data-table td {
  padding: 10px 14px;
  text-align: left;
  border-bottom: 1px solid #e3e8ef;
}

.data-table thead th {
  background: var(--color-primary);
  color: var(--color-cloud);
  font-weight: 700;
  letter-spacing: 0.04em;
  font-size: 13px;
}

.data-table tbody tr:hover { background: rgba(212, 175, 55, 0.08); }

/* ---------- 11. 页头与悬浮胶囊导航 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 150;
  padding: 14px 20px 10px;
}

.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 220;
  padding: 10px 20px;
  background: var(--color-gold);
  color: var(--color-primary);
  font-weight: 700;
  border-radius: var(--radius-md);
  text-decoration: none;
  box-shadow: 0 6px 18px rgba(11, 29, 58, 0.3);
  transform: translateY(-160%);
  transition: transform 0.25s ease;
}

.skip-link:focus-visible { transform: translateY(0); }

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 0;
  height: 3px;
  z-index: 210;
  background: linear-gradient(90deg, var(--color-gold) 0%, var(--color-red) 55%, var(--color-gold-light) 100%);
  border-radius: 0 3px 3px 0;
  pointer-events: none;
}

.header-capsule {
  position: relative;
  max-width: 1180px;
  margin-inline: auto;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 10px 10px 10px 20px;
  background:
    radial-gradient(120% 160% at 85% 0%, rgba(212, 175, 55, 0.12) 0%, transparent 42%),
    linear-gradient(115deg, var(--color-primary) 0%, #132a4d 64%, var(--color-primary-light) 100%);
  border: 1px solid rgba(212, 175, 55, 0.35);
  border-radius: var(--radius-pill);
  box-shadow: var(--shadow-float);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  flex: 0 0 auto;
}

.brand__emblem {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  transform: rotate(45deg);
  border-radius: 12px;
  background: linear-gradient(135deg, var(--color-gold) 0%, var(--color-red-light) 100%);
  box-shadow: 0 6px 16px rgba(212, 175, 55, 0.35);
}

.brand__emblem-letter {
  transform: rotate(-45deg);
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 900;
  color: var(--color-primary);
  line-height: 1;
}

.brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
}

.brand__name {
  font-family: var(--font-display);
  font-size: 22px;
  letter-spacing: 0.02em;
  color: var(--color-white);
  white-space: nowrap;
}

.brand__kok { color: var(--color-gold); }

.brand__slogan {
  font-size: 10px;
  letter-spacing: 0.32em;
  color: rgba(245, 247, 250, 0.58);
  margin-top: 2px;
  white-space: nowrap;
}

.site-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  margin-inline: auto;
}

.site-nav__link {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding: 9px 15px;
  border-radius: var(--radius-pill);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.03em;
  color: rgba(245, 247, 250, 0.8);
  text-decoration: none;
  white-space: nowrap;
  transition:
    color var(--transition-base),
    background var(--transition-base),
    box-shadow var(--transition-base);
}

.site-nav__link:hover {
  color: var(--color-gold-light);
  background: rgba(212, 175, 55, 0.12);
}

.site-nav__link[aria-current="page"] {
  color: var(--color-primary);
  background: linear-gradient(135deg, var(--color-gold) 0%, var(--color-gold-light) 100%);
  box-shadow: 0 4px 12px rgba(212, 175, 55, 0.4);
  font-weight: 800;
}

.header-entry {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
  padding: 10px 20px;
  border-radius: var(--radius-pill);
  background: rgba(214, 40, 40, 0.16);
  border: 1px solid rgba(214, 40, 40, 0.55);
  color: var(--color-red-light);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-decoration: none;
  transition:
    background var(--transition-base),
    color var(--transition-base),
    border-color var(--transition-base),
    transform var(--transition-base);
}

.header-entry::before {
  content: '';
  width: 8px;
  height: 8px;
  background: var(--color-red-light);
  transform: rotate(45deg);
}

.header-entry:hover {
  background: rgba(214, 40, 40, 0.28);
  color: #FFCFCF;
  border-color: var(--color-red-light);
}

.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
  width: 44px;
  height: 44px;
  padding: 0;
  margin-left: auto;
  flex: 0 0 auto;
  background: rgba(245, 247, 250, 0.08);
  border: 1px solid rgba(212, 175, 55, 0.4);
  border-radius: 50%;
  cursor: pointer;
  transition:
    background var(--transition-base),
    border-color var(--transition-base);
}

.nav-toggle:hover { background: rgba(212, 175, 55, 0.16); }

.nav-toggle__bar {
  width: 18px;
  height: 2px;
  border-radius: 2px;
  background: var(--color-cloud);
  transition:
    transform var(--transition-base),
    opacity var(--transition-base);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- 12. 平板与移动端导航 ---------- */
@media (max-width: 1100px) and (min-width: 881px) {
  .site-nav__link { padding: 8px 10px; font-size: 13px; }
  .brand__name { font-size: 19px; }
  .header-capsule { gap: 8px; padding-left: 14px; }
}

@media (max-width: 880px) {
  .site-header { padding: 10px 12px 8px; }
  .header-capsule {
    border-radius: 22px;
    padding: 8px 8px 8px 14px;
    gap: 8px;
  }
  .brand__emblem { width: 38px; height: 38px; border-radius: 10px; }
  .brand__name { font-size: 19px; }
  .header-entry { display: none; }
  .nav-toggle { display: inline-flex; }

  .site-nav {
    position: absolute;
    top: calc(100% + 10px);
    left: 0;
    right: 0;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
    margin: 0;
    padding: 14px;
    background:
      radial-gradient(120% 140% at 88% 0%, rgba(212, 175, 55, 0.14) 0%, transparent 46%),
      linear-gradient(150deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
    border: 1px solid rgba(212, 175, 55, 0.4);
    border-radius: 20px;
    box-shadow: var(--shadow-float);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition:
      opacity var(--transition-base),
      transform var(--transition-base),
      visibility var(--transition-base);
  }

  .site-nav[data-open] {
    opacity: 1;
    visibility: visible;
    transform: none;
  }

  .site-nav__link {
    padding: 12px 18px;
    font-size: 15px;
    justify-content: flex-start;
    color: rgba(245, 247, 250, 0.82);
    border-radius: 12px;
  }

  .site-nav__link[aria-current="page"] { color: var(--color-primary); }
}

@media (max-width: 420px) {
  .brand__slogan { display: none; }
  .brand__name { font-size: 17px; }
}

#main-content { scroll-margin-top: 24px; }

/* ---------- 13. 页脚 ---------- */
.site-footer {
  position: relative;
  color: rgba(245, 247, 250, 0.75);
  background-image:
    linear-gradient(rgba(245, 247, 250, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(245, 247, 250, 0.035) 1px, transparent 1px),
    radial-gradient(90% 70% at 18% 10%, rgba(212, 175, 55, 0.13) 0%, transparent 48%),
    linear-gradient(160deg, #091729 0%, var(--color-primary) 55%, #102143 100%);
  background-size:
    44px 44px,
    44px 44px,
    auto,
    auto;
  background-repeat:
    repeat,
    repeat,
    no-repeat,
    no-repeat;
  padding-bottom: 32px;
}

.site-footer__accent {
  height: 4px;
  background: linear-gradient(90deg, transparent 2%, var(--color-gold) 24%, var(--color-red) 52%, var(--color-gold-light) 78%, transparent 98%);
}

.footer-grid {
  display: grid;
  grid-template-columns: minmax(260px, 1.4fr) 0.8fr 0.8fr minmax(220px, 1fr);
  gap: 44px;
  padding-top: 56px;
  padding-bottom: 40px;
}

@media (max-width: 1024px) {
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 36px 32px; }
}

@media (max-width: 600px) {
  .footer-grid { grid-template-columns: 1fr; gap: 32px; padding-top: 40px; }
}

.footer-brand__link {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.footer-brand__emblem {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  transform: rotate(45deg);
  border-radius: 13px;
  background: linear-gradient(135deg, var(--color-gold) 0%, var(--color-red-light) 100%);
  box-shadow: 0 6px 18px rgba(212, 175, 55, 0.3);
}

.footer-brand__emblem-core {
  transform: rotate(-45deg);
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 900;
  color: var(--color-primary);
  line-height: 1;
}

.footer-brand__text {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.footer-brand__name {
  font-family: var(--font-display);
  font-size: 26px;
  letter-spacing: 0.03em;
  color: var(--color-white);
  line-height: 1.1;
}

.footer-brand__kok { color: var(--color-gold); }

.footer-brand__slogan {
  font-size: 11px;
  letter-spacing: 0.32em;
  color: var(--color-gold);
  line-height: 1.4;
}

.footer-brand__trust {
  margin-top: 18px;
  max-width: 300px;
  font-size: 14px;
  line-height: 1.85;
  color: rgba(245, 247, 250, 0.62);
  border-left: 3px solid rgba(212, 175, 55, 0.6);
  padding-left: 14px;
}

.footer-col { min-width: 0; }
.footer-col--contact { min-width: 0; }

.footer-col__title {
  margin: 0 0 18px;
  padding-bottom: 8px;
  font-family: var(--font-display);
  font-size: 15px;
  letter-spacing: 0.14em;
  color: var(--color-gold);
  border-bottom: 1px solid rgba(212, 175, 55, 0.22);
}

.footer-col__title::before {
  content: '◆';
  font-size: 8px;
  vertical-align: 2px;
  margin-right: 8px;
  color: var(--color-red-light);
}

.footer-links {
  list-style: none;
  display: grid;
  gap: 10px;
}

.footer-links__item { margin: 0; }

.footer-links a {
  display: inline-block;
  color: rgba(245, 247, 250, 0.72);
  font-size: 14px;
  text-decoration: none;
  transition:
    color var(--transition-base),
    transform var(--transition-base);
}

.footer-links a:hover {
  color: var(--color-gold-light);
  transform: translateX(4px);
}

.footer-contact {
  list-style: none;
  display: grid;
  gap: 16px;
}

.footer-contact__item {
  display: flex;
  gap: 12px;
  font-size: 14px;
  line-height: 1.6;
  color: rgba(245, 247, 250, 0.78);
}

.footer-contact__item::before {
  content: '';
  flex: none;
  width: 7px;
  height: 7px;
  margin-top: 8px;
  background: linear-gradient(135deg, var(--color-gold), var(--color-red-light));
  transform: rotate(45deg);
  border-radius: 1px;
}

.footer-contact__label {
  flex: 0 0 auto;
  min-width: 28px;
  color: var(--color-gold);
  font-weight: 700;
}

.footer-contact__value { word-break: break-word; }

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 20px;
  padding-top: 22px;
  border-top: 1px dashed rgba(212, 175, 55, 0.32);
  font-size: 13px;
  color: rgba(245, 247, 250, 0.55);
}

.footer-bottom__copy { margin: 0; }
.footer-bottom__icp { margin: 0; letter-spacing: 0.06em; }

/* ---------- 14. 返回顶部 ---------- */
.back-to-top {
  position: fixed;
  right: 26px;
  bottom: 26px;
  z-index: 160;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 50px;
  height: 50px;
  padding: 0;
  border: 1px solid rgba(212, 175, 55, 0.55);
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary) 0%, #18335c 100%);
  color: var(--color-gold-light);
  cursor: pointer;
  box-shadow: 0 10px 28px rgba(11, 29, 58, 0.38);
  opacity: 0;
  visibility: hidden;
  transform: translateY(14px);
  transition:
    opacity var(--transition-base),
    transform var(--transition-base),
    visibility var(--transition-base),
    background var(--transition-base);
}

.back-to-top:hover {
  background: linear-gradient(135deg, #142d52 0%, var(--color-primary-light) 100%);
  border-color: var(--color-gold-light);
}

.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: none;
}

.back-to-top__icon { font-size: 22px; line-height: 1; }

/* ---------- 15. 滚动显现 ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(26px);
  transition:
    opacity 0.6s ease,
    transform 0.6s ease;
}

[data-reveal][data-reveal-visible] {
  opacity: 1;
  transform: none;
}

/* ---------- 16. 无障碍与减少动态 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    transition-delay: 0ms !important;
  }

  [data-reveal] {
    opacity: 1;
    transform: none;
  }

  .back-to-top { transition: none; }
}

@media (max-width: 640px) {
  .container { padding-inline: 16px; }
  .section { padding-block: 52px; }
  .card { padding: 22px; }
  .print-frame { padding: 20px; }
}