/* ============================================================
   亿兆竞技 · Site Kit 共享样式
   设计指纹：93f4fe9c309baa35
   母题：风马旗命令栏 · 纵向叙事长卷
   ============================================================ */

/* ---------- 1. 设计变量 ---------- */
:root {
  --color-primary: #0A1E3C;
  --color-primary-deep: #081829;
  --color-primary-raised: #0D2447;
  --color-gold: #F5B500;
  --color-accent: #FF6B35;
  --color-white: #F7F9FC;
  --color-muted: #B0C4DE;
  --color-red: #D22B2B;
  --color-green: #2E8B57;
  --color-yellow: #FCE83A;
  --color-link: #1E90FF;
  --color-glass: rgba(255, 255, 255, 0.08);
  --color-glass-strong: rgba(255, 255, 255, 0.13);

  --font-sans: "Noto Sans SC", -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "SimSun", Georgia, serif;
  --font-mono: "Roboto Mono", "SF Mono", "Cascadia Mono", "Consolas", monospace;

  --container-w: 1200px;
  --container-wide: 1440px;
  --container-narrow: 860px;

  --header-h: 72px;
  --header-h-mobile: 62px;

  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-5: 48px;
  --space-6: 64px;
  --space-7: 96px;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 18px;
  --radius-xl: 28px;

  --transition-fast: 180ms ease;
  --transition-base: 260ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 420ms cubic-bezier(0.22, 1, 0.36, 1);

  color-scheme: dark;
}

/* ---------- 2. Reset 与基础 ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 12px);
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: clip;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  color: var(--color-white);
  background-color: var(--color-primary);
  background-image:
    radial-gradient(ellipse at 80% -10%, rgba(30, 144, 255, 0.08), transparent 60%),
    radial-gradient(ellipse at 0% 40%, rgba(245, 181, 0, 0.04), transparent 45%);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a {
  color: var(--color-link);
  text-decoration: none;
}

img,
picture,
svg,
video {
  display: block;
  max-width: 100%;
  height: auto;
}

button,
input,
select,
textarea {
  font: inherit;
  color: inherit;
}

ul,
ol {
  list-style: none;
}

::selection {
  background: var(--color-gold);
  color: var(--color-primary);
}

:focus-visible {
  outline: 2px solid var(--color-gold);
  outline-offset: 2px;
  border-radius: 2px;
}

/* ---------- 3. 中文排版 ---------- */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-sans);
  font-weight: 700;
  line-height: 1.25;
  color: var(--color-white);
  overflow-wrap: break-word;
}

p {
  overflow-wrap: break-word;
}

.serif {
  font-family: var(--font-serif);
}

.mono {
  font-family: var(--font-mono);
}

.eyebrow {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 15px;
  letter-spacing: 0.03em;
  color: var(--color-gold);
}

.stat {
  font-family: var(--font-mono);
  font-size: 28px;
  font-weight: 600;
  line-height: 1.2;
  color: var(--color-gold);
  font-variant-numeric: tabular-nums;
}

.text-gold { color: var(--color-gold); }
.text-accent { color: var(--color-accent); }
.text-muted { color: var(--color-muted); }
.text-white { color: var(--color-white); }
.text-center { text-align: center; }

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

.rich-text {
  color: var(--color-muted);
  font-size: 16px;
  line-height: 1.85;
}

.rich-text p {
  margin-bottom: 1.4em;
}

.rich-text h2,
.rich-text h3,
.rich-text h4 {
  margin-top: 1.8em;
  margin-bottom: 0.7em;
  color: var(--color-white);
}

.rich-text a {
  color: var(--color-link);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.rich-text blockquote {
  margin: 1.6em 0;
  padding: 12px 20px;
  border-left: 3px solid var(--color-gold);
  font-family: var(--font-serif);
  font-style: italic;
  color: var(--color-white);
  background: var(--color-glass);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.rich-text ul,
.rich-text ol {
  margin: 0 0 1.4em 1.4em;
}

.rich-text li {
  margin-bottom: 0.4em;
}

.rich-text code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--color-glass);
  padding: 0.15em 0.5em;
  border-radius: 4px;
}

/* ---------- 4. 布局工具 ---------- */
.container {
  width: min(var(--container-w), 100% - 48px);
  margin-inline: auto;
}

.container--wide {
  width: min(var(--container-wide), 100% - 32px);
  margin-inline: auto;
}

.container--narrow {
  width: min(var(--container-narrow), 100% - 48px);
  margin-inline: auto;
}

.site-main {
  flex: 1;
  width: 100%;
}

.section {
  padding-block: var(--space-6);
}

.section--tight {
  padding-block: var(--space-4);
}

.section--loose {
  padding-block: var(--space-7);
}

.section__head {
  display: grid;
  gap: 8px;
  margin-bottom: var(--space-4);
}

.section__number {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--color-gold);
  text-transform: uppercase;
}

.section__title {
  font-size: clamp(26px, 4vw, 40px);
  letter-spacing: 0.02em;
}

.grid {
  display: grid;
  gap: var(--space-4);
}

.grid--2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

/* ---------- 5. 通用组件 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 24px;
  border-radius: 8px;
  border: 1px solid transparent;
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
  transition:
    transform var(--transition-fast),
    box-shadow var(--transition-fast),
    background-color var(--transition-fast),
    border-color var(--transition-fast);
}

.btn:active {
  transform: translateY(1px) scale(0.98);
}

.btn--accent {
  background: var(--color-accent);
  color: #ffffff;
  box-shadow: 0 4px 20px rgba(255, 107, 53, 0.28);
}

.btn--accent:hover,
.btn--accent:focus-visible {
  background: #e95f2c;
  box-shadow: 0 8px 30px rgba(255, 107, 53, 0.38);
  transform: translateY(-1px);
  color: #ffffff;
}

.btn--gold {
  background: var(--color-gold);
  color: var(--color-primary);
  box-shadow: 0 4px 20px rgba(245, 181, 0, 0.2);
}

.btn--gold:hover,
.btn--gold:focus-visible {
  background: #ffcc33;
  box-shadow: 0 8px 30px rgba(245, 181, 0, 0.3);
  transform: translateY(-1px);
  color: var(--color-primary);
}

.btn--ghost {
  background: transparent;
  border-color: rgba(247, 249, 252, 0.35);
  color: var(--color-white);
}

.btn--ghost:hover,
.btn--ghost:focus-visible {
  border-color: var(--color-gold);
  color: var(--color-gold);
}

.btn--glass {
  background: var(--color-glass);
  border-color: rgba(255, 255, 255, 0.16);
  color: var(--color-white);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.btn--glass:hover,
.btn--glass:focus-visible {
  background: var(--color-glass-strong);
  border-color: var(--color-gold);
  color: var(--color-gold);
}

.card {
  background: var(--color-glass);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  position: relative;
  transition:
    border-color var(--transition-base),
    transform var(--transition-base),
    box-shadow var(--transition-base),
    background-color var(--transition-base);
}

.card:hover {
  border-color: rgba(245, 181, 0, 0.55);
  transform: translateY(-4px);
  box-shadow: 0 16px 40px rgba(0, 0, 0, 0.25);
}

.card + .card {
  margin-top: var(--space-3);
}

.glass-card {
  background: var(--color-glass);
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 12px;
  border-radius: 999px;
  font-family: var(--font-sans);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.04em;
  line-height: 1.5;
  white-space: nowrap;
}

.tag--gold {
  background: rgba(245, 181, 0, 0.14);
  border: 1px solid rgba(245, 181, 0, 0.35);
  color: var(--color-gold);
}

.tag--accent {
  background: rgba(255, 107, 53, 0.14);
  border: 1px solid rgba(255, 107, 53, 0.35);
  color: var(--color-accent);
}

.tag--green {
  background: rgba(46, 139, 87, 0.16);
  border: 1px solid rgba(46, 139, 87, 0.4);
  color: #6dd39a;
}

.tag--red {
  background: rgba(210, 43, 43, 0.15);
  border: 1px solid rgba(210, 43, 43, 0.4);
  color: #e67a7a;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 2px 10px;
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.08em;
  color: var(--color-muted);
  background: var(--color-glass);
  border: 1px solid rgba(255, 255, 255, 0.12);
}

.badge--gold {
  background: rgba(245, 181, 0, 0.14);
  border-color: rgba(245, 181, 0, 0.35);
  color: var(--color-gold);
}

.breadcrumbs {
  padding-block: var(--space-3);
}

.breadcrumbs__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.breadcrumbs__item {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--color-muted);
}

.breadcrumbs__link {
  color: var(--color-muted);
  transition: color var(--transition-fast);
}

.breadcrumbs__link:hover {
  color: var(--color-gold);
}

.breadcrumbs__sep {
  color: rgba(255, 255, 255, 0.3);
  user-select: none;
}

.breadcrumbs__item[aria-current="page"] {
  color: var(--color-gold);
  font-weight: 500;
}

.image-frame {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-md);
  background-color: rgba(255, 255, 255, 0.05);
  background-image: linear-gradient(45deg, rgba(255, 255, 255, 0.035) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, 0.035) 50%, rgba(255, 255, 255, 0.035) 75%, transparent 75%);
  background-size: 28px 28px;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.image-frame--hero {
  aspect-ratio: 16 / 7;
}

.image-frame--card {
  aspect-ratio: 4 / 3;
}

.image-frame--wide {
  aspect-ratio: 21 / 9;
}

/* ---------- 6. 页头 ---------- */
.skip-link {
  position: fixed;
  top: -100px;
  left: 16px;
  z-index: 600;
  padding: 10px 22px;
  background: var(--color-gold);
  color: var(--color-primary);
  font-size: 14px;
  font-weight: 700;
  border-radius: 0 0 12px 12px;
  text-decoration: none;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3);
  transition: top var(--transition-fast);
}

.skip-link:focus,
.skip-link:focus-visible {
  top: 0;
  outline: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 200;
  background: rgba(10, 30, 60, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.site-header::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 1;
  background: rgba(4, 13, 28, 0.6);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-base), visibility var(--transition-base);
  pointer-events: none;
}

.site-header:has(.site-nav[data-open="true"])::after {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}

.scroll-progress {
  position: absolute;
  top: 100%;
  left: 0;
  width: 100%;
  height: 3px;
  z-index: 10;
  background: linear-gradient(90deg, var(--color-gold), var(--color-accent));
  transform: scaleX(0);
  transform-origin: 0 50%;
  pointer-events: none;
}

.site-header__flag {
  display: flex;
  height: 4px;
  position: relative;
  z-index: 3;
}

.site-header__flag-bar {
  flex: 1;
  min-width: 0;
}

.site-header__flag-bar--blue { background: var(--color-link); }
.site-header__flag-bar--gold { background: var(--color-gold); }
.site-header__flag-bar--red { background: var(--color-red); }
.site-header__flag-bar--green { background: var(--color-green); }
.site-header__flag-bar--yellow { background: var(--color-yellow); }

.site-header__inner {
  position: relative;
  z-index: 3;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  height: var(--header-h);
}

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

.site-brand__mark {
  display: flex;
  gap: 2px;
  width: 40px;
  height: 28px;
  padding: 2px;
  background: var(--color-glass);
  border: 1px solid rgba(255, 255, 255, 0.08);
  clip-path: polygon(6px 0, 100% 0, calc(100% - 6px) 100%, 0 100%);
}

.site-brand__cell {
  flex: 1;
  border-radius: 1px;
}

.site-brand__cell--gold {
  background: var(--color-gold);
}

.site-brand__cell--orange {
  background: var(--color-accent);
}

.site-brand__text {
  display: grid;
  gap: 1px;
  line-height: 1.1;
}

.site-brand__name {
  font-size: 19px;
  font-weight: 800;
  letter-spacing: 0.08em;
  color: var(--color-white);
}

.site-brand__en {
  font-family: var(--font-mono);
  font-size: 9px;
  letter-spacing: 0.3em;
  color: var(--color-gold);
  text-transform: uppercase;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 6px;
}

.site-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.site-nav__item {
  margin: 0;
  padding: 0;
}

.site-nav__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 9px 13px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-muted);
  text-decoration: none;
  position: relative;
  transition:
    color var(--transition-fast),
    background-color var(--transition-fast);
}

.site-nav__link:hover {
  color: var(--color-white);
  background: var(--color-glass);
}

.site-nav__link[aria-current="page"] {
  color: var(--color-gold);
  background: rgba(245, 181, 0, 0.08);
}

.site-nav__link[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 13px;
  right: 13px;
  bottom: 5px;
  height: 2px;
  border-radius: 2px;
  background: var(--color-gold);
}

.site-nav__index {
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: 500;
  letter-spacing: 0.06em;
  color: rgba(245, 181, 0, 0.75);
}

.site-nav__label {
  white-space: nowrap;
}

.site-nav__cta {
  margin-left: 12px;
  padding: 8px 20px;
  font-size: 13px;
}

.site-nav__cta-arrow {
  display: inline-block;
  transition: transform var(--transition-fast);
}

.site-nav__cta:hover .site-nav__cta-arrow,
.site-nav__cta:focus-visible .site-nav__cta-arrow {
  transform: translateX(4px);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 8px 14px;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  background: var(--color-glass);
  color: var(--color-white);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition:
    background-color var(--transition-fast),
    border-color var(--transition-fast);
}

.nav-toggle:hover {
  background: var(--color-glass-strong);
  border-color: rgba(245, 181, 0, 0.5);
}

.nav-toggle[aria-expanded="true"] {
  background: rgba(245, 181, 0, 0.12);
  border-color: var(--color-gold);
  color: var(--color-gold);
}

.nav-toggle__lines {
  display: grid;
  gap: 4px;
  flex-shrink: 0;
}

.nav-toggle__line {
  display: block;
  width: 18px;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(2) {
  opacity: 0;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__line:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

.nav-toggle__text {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-muted);
  transition: color var(--transition-fast);
}

.nav-toggle:hover .nav-toggle__text {
  color: var(--color-white);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__text {
  color: var(--color-gold);
}

/* ---------- 7. 页脚 ---------- */
.site-footer {
  position: relative;
  overflow: hidden;
  background: linear-gradient(180deg, #0D2447 0%, #081829 100%);
  border-top: 1px solid rgba(255, 255, 255, 0.08);
}

.site-footer::before {
  content: "YIZHAO";
  position: absolute;
  right: -20px;
  bottom: -30px;
  z-index: 0;
  font-family: var(--font-mono);
  font-size: clamp(120px, 18vw, 240px);
  font-weight: 800;
  letter-spacing: 0.2em;
  color: rgba(255, 255, 255, 0.02);
  pointer-events: none;
  user-select: none;
}

.site-footer__flag {
  display: flex;
  height: 6px;
}

.site-footer__flag-bar {
  flex: 1;
  min-width: 0;
}

.site-footer__flag-bar + .site-footer__flag-bar {
  border-left: 3px solid var(--color-primary);
}

.site-footer__flag-bar--blue { background: var(--color-link); }
.site-footer__flag-bar--gold { background: var(--color-gold); }
.site-footer__flag-bar--red { background: var(--color-red); }
.site-footer__flag-bar--green { background: var(--color-green); }
.site-footer__flag-bar--yellow { background: var(--color-yellow); }

.site-footer__inner {
  position: relative;
  z-index: 1;
  padding-block: var(--space-5) var(--space-3);
}

.site-footer__top {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1.2fr;
  gap: 40px;
  margin-bottom: var(--space-5);
}

.site-footer__brand {
  display: grid;
  align-content: start;
  gap: 6px;
}

.site-footer__logo {
  display: inline-block;
  width: fit-content;
  font-size: 28px;
  font-weight: 800;
  letter-spacing: 0.1em;
  color: var(--color-white);
  text-decoration: none;
  border-bottom: 2px solid var(--color-gold);
  padding-bottom: 6px;
}

.site-footer__slogan {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 14px;
  color: var(--color-gold);
  margin-top: 8px;
}

.site-footer__trust {
  font-size: 13px;
  line-height: 1.7;
  color: var(--color-muted);
  max-width: 360px;
  margin-top: 14px;
}

.site-footer__col {
  display: grid;
  align-content: start;
  gap: 0;
}

.site-footer__heading {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-gold);
  margin-bottom: 14px;
}

.site-footer__heading::before {
  content: "";
  width: 20px;
  height: 3px;
  border-radius: 2px;
  background: var(--color-accent);
}

.site-footer__nav {
  display: grid;
  gap: 4px;
}

.site-footer__link {
  display: inline-flex;
  align-items: center;
  width: fit-content;
  padding-block: 3px;
  font-size: 14px;
  color: var(--color-muted);
  text-decoration: none;
  transition: color var(--transition-fast), transform var(--transition-fast);
}

.site-footer__link:hover {
  color: var(--color-gold);
  transform: translateX(4px);
}

.site-footer__link--inline {
  padding-block: 0;
  font-size: 12px;
  transition: color var(--transition-fast);
}

.site-footer__link--inline:hover {
  transform: none;
}

.site-footer__info {
  font-size: 14px;
  line-height: 1.9;
  color: var(--color-muted);
}

.site-footer__icp {
  display: inline-block;
  margin-top: 12px;
  padding: 3px 12px;
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--color-muted);
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.site-footer__bottom {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 8px 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 20px;
  font-size: 12px;
  color: rgba(176, 196, 222, 0.66);
}

.site-footer__copyright {
  margin: 0;
}

.site-footer__legal {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin: 0;
}

.site-footer__dot {
  color: rgba(255, 255, 255, 0.25);
  user-select: none;
}

.site-footer__legal .site-footer__link {
  color: rgba(176, 196, 222, 0.75);
}

.site-footer__legal .site-footer__link:hover {
  color: var(--color-gold);
}

.back-to-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 90;
  width: 44px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.16);
  background: rgba(13, 36, 71, 0.9);
  color: var(--color-gold);
  font-size: 18px;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(16px);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  transition:
    opacity var(--transition-base),
    transform var(--transition-base),
    visibility var(--transition-base),
    background-color var(--transition-base),
    color var(--transition-base);
}

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

.back-to-top:hover,
.back-to-top:focus-visible {
  background: var(--color-gold);
  color: var(--color-primary);
  border-color: var(--color-gold);
}

.back-to-top__icon {
  display: inline-block;
  line-height: 1;
}

/* ---------- 8. 显现动画 ---------- */
[data-reveal] {
  opacity: 0;
  transform: translateY(24px);
  transition:
    opacity 0.7s cubic-bezier(0.22, 1, 0.36, 1),
    transform 0.7s cubic-bezier(0.22, 1, 0.36, 1);
  transition-delay: var(--reveal-delay, 0ms);
}

[data-reveal].is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- 9. 响应式 ---------- */
@media (max-width: 1023px) {
  :root {
    --header-h: 62px;
  }

  .site-header__inner {
    height: var(--header-h-mobile);
  }

  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    z-index: 2;
    width: min(340px, 88vw);
    height: calc(100vh - var(--header-h-mobile));
    height: calc(100dvh - var(--header-h-mobile));
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 24px 20px 28px;
    background: rgba(8, 24, 48, 0.98);
    border-right: 1px solid rgba(255, 255, 255, 0.1);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: 16px 0 50px rgba(0, 0, 0, 0.4);
    transform: translateX(-105%);
    visibility: hidden;
    transition: transform var(--transition-base), visibility var(--transition-base);
    overflow-y: auto;
  }

  .site-nav::before {
    content: "站点索引 / INDEX";
    font-family: var(--font-mono);
    font-size: 11px;
    letter-spacing: 0.2em;
    color: var(--color-gold);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    padding-bottom: 12px;
    margin-bottom: 18px;
  }

  .site-nav[data-open="true"] {
    transform: translateX(0);
    visibility: visible;
  }

  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
    flex: 1;
  }

  .site-nav__link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 13px 16px;
    font-size: 16px;
  }

  .site-nav__link[aria-current="page"]::after {
    left: 16px;
    right: 16px;
    bottom: 6px;
  }

  .site-nav__cta {
    margin-left: 0;
    margin-top: 20px;
    justify-content: center;
    padding: 12px 24px;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .grid--3,
  .grid--4 {
    grid-template-columns: repeat(2, 1fr);
  }

  .site-footer__top {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .site-footer__brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .container,
  .container--narrow,
  .container--wide {
    width: min(100% - 32px, 100%);
  }

  .site-brand__mark {
    width: 34px;
    height: 24px;
  }

  .site-brand__name {
    font-size: 16px;
  }

  .site-brand__en {
    font-size: 8px;
  }

  .site-nav {
    width: 86vw;
    padding: 20px 16px 24px;
  }

  .grid--2,
  .grid--3,
  .grid--4 {
    grid-template-columns: 1fr;
  }

  .site-footer__top {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .site-footer__bottom {
    flex-direction: column;
    align-items: flex-start;
    gap: 6px;
  }

  .back-to-top {
    right: 14px;
    bottom: 14px;
  }
}

/* ---------- 10. 可访问性与减少动效 ---------- */
@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;
    scroll-behavior: auto !important;
  }

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