/* =========================================================
   滕博会FN · /assets/site.css
   共享外壳：reset / 变量 / 头部 / 页脚 / 通用组件
   ========================================================= */

/* ---------- 1. Reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

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

body,
h1, h2, h3, h4, h5, h6,
p, figure, blockquote, dl, dd, ul, ol {
  margin: 0;
}

ul, ol { padding: 0; list-style: none; }

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

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

button {
  background: none;
  border: 0;
  cursor: pointer;
}

a { color: inherit; }

table { border-collapse: collapse; width: 100%; }

/* ---------- 2. 设计变量 ---------- */
:root {
  /* 品牌色板 */
  --abyss-900: #061826;
  --abyss-800: #091E2E;
  --abyss-700: #0D2A3F;
  --abyss-500: #173F5C;
  --ink-050: #F3F7FA;
  --steel-400: #8CA3B5;
  --signal-orange: #FF6B35;
  --signal-orange-deep: #E4551F;
  --celadon-400: #4FD1B0;
  --warm-gold: #F4C96B;
  --alert-coral: #FF8A7A;
  --paper-100: #FAF7F0;
  --paper-ink: #1B2A35;
  --line-300: #2B4A61;

  /* 语义映射 */
  --bg: var(--abyss-900);
  --bg-panel: var(--abyss-700);
  --fg: var(--ink-050);
  --fg-muted: var(--steel-400);
  --accent: var(--signal-orange);
  --accent-alt: var(--celadon-400);
  --line: var(--line-300);
  --line-soft: rgba(43, 74, 97, 0.66);

  /* 字体族 */
  --font-display: "Sora", "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "Inter", "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --font-serif: "Noto Serif SC", "Songti SC", "SimSun", Georgia, serif;

  /* 1.25 倍字号阶梯 */
  --t-12: 0.75rem;
  --t-14: 0.875rem;
  --t-16: 1rem;
  --t-20: 1.25rem;
  --t-25: 1.5625rem;
  --t-32: 2rem;
  --t-40: 2.5rem;
  --t-64: 4rem;
  --t-96: 6rem;
  --t-144: 9rem;

  /* 布局 */
  --wrap: 1180px;
  --gutter: clamp(1.125rem, 4vw, 2.75rem);
  --header-h: 56px;

  /* 形状与阴影 */
  --r-sm: 6px;
  --r-md: 12px;
  --r-lg: 20px;
  --r-pill: 999px;
  --shadow-soft: 0 24px 60px -34px rgba(0, 0, 0, 0.92);
  --ease: cubic-bezier(0.2, 0.7, 0.3, 1);
}

/* ---------- 3. 基础排版 ---------- */
body {
  min-height: 100vh;
  padding-top: calc(16px + var(--header-h) + 20px);
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-body);
  font-size: var(--t-16);
  line-height: 1.75;
  letter-spacing: 0.005em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.02em;
  text-wrap: balance;
  color: var(--fg);
}

p { text-wrap: pretty; }

strong, b { font-weight: 700; }

::selection {
  background: var(--signal-orange);
  color: var(--abyss-900);
}

:where(a, button, [tabindex], summary):focus-visible {
  outline: 2px solid var(--signal-orange);
  outline-offset: 3px;
}

#main-content {
  display: block;
  outline: none;
  scroll-margin-top: calc(16px + var(--header-h) + 20px);
}

/* ---------- 4. 布局容器 ---------- */
.container {
  width: min(var(--wrap), 100% - (var(--gutter) * 2));
  margin-inline: auto;
}

.section {
  position: relative;
  padding-block: clamp(3rem, 8vw, 6.5rem);
}

.section--tight { padding-block: clamp(2rem, 5vw, 3.5rem); }

.section--panel { background: var(--bg-panel); }

.section--paper {
  background: var(--paper-100);
  color: var(--paper-ink);
}

.section--paper h1,
.section--paper h2,
.section--paper h3,
.section--paper h4 { color: var(--paper-ink); }

.section--paper .lede,
.section--paper .card__text { color: #4A5C68; }

.grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: clamp(1rem, 2.5vw, 1.75rem);
}

.grid--auto {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: clamp(1rem, 2.5vw, 1.75rem);
}

.grid--aside {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(1.25rem, 3vw, 2.5rem);
}

@media (min-width: 900px) {
  .grid { grid-template-columns: repeat(12, minmax(0, 1fr)); }
}

@media (min-width: 960px) {
  .grid--aside { grid-template-columns: minmax(0, 2.35fr) minmax(0, 1fr); }
}

/* ---------- 5. 排版工具 ---------- */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent-alt);
}

.eyebrow::before {
  content: "";
  width: 22px;
  height: 1px;
  background: currentColor;
}

.measure { max-width: 66ch; }

.lede {
  max-width: 64ch;
  font-size: clamp(1.0625rem, 1.5vw, var(--t-20));
  line-height: 1.7;
  color: var(--fg-muted);
}

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
}

.rule {
  height: 1px;
  border: 0;
  margin-block: clamp(1.5rem, 4vw, 2.5rem);
  background: linear-gradient(90deg, var(--line), rgba(43, 74, 97, 0));
}

.serif-note {
  max-width: 46ch;
  padding-left: 1rem;
  border-left: 2px solid var(--signal-orange);
  font-family: var(--font-serif);
  font-size: var(--t-20);
  line-height: 1.6;
  color: var(--celadon-400);
}

/* ---------- 6. 按钮 ---------- */
.btn {
  --btn-bg: var(--abyss-500);
  --btn-fg: var(--ink-050);
  --btn-bd: var(--line);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  border: 1px solid var(--btn-bd);
  border-radius: var(--r-pill);
  background: var(--btn-bg);
  color: var(--btn-fg);
  font-family: var(--font-body);
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1.2;
  text-decoration: none;
  white-space: nowrap;
  transition: background 150ms var(--ease), color 150ms var(--ease),
    border-color 150ms var(--ease), transform 150ms var(--ease),
    box-shadow 150ms var(--ease);
}

.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn--signal {
  --btn-bg: var(--signal-orange-deep);
  --btn-fg: #FFFFFF;
  --btn-bd: transparent;
  box-shadow: 0 12px 28px -18px rgba(255, 107, 53, 0.95);
}

.btn--signal:hover {
  --btn-bg: var(--signal-orange);
  --btn-fg: var(--abyss-900);
}

.btn--ghost {
  --btn-bg: transparent;
  --btn-fg: var(--ink-050);
  --btn-bd: var(--line);
}

.btn--ghost:hover {
  --btn-bg: rgba(79, 209, 176, 0.1);
  --btn-fg: var(--celadon-400);
  --btn-bd: var(--celadon-400);
}

.btn--sm {
  padding: 0.5rem 0.9rem;
  font-size: 0.8125rem;
}

.btn--block { width: 100%; }

.btn[disabled],
.btn[aria-disabled="true"] {
  opacity: 0.42;
  pointer-events: none;
  transform: none;
}

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  color: var(--celadon-400);
  text-decoration: none;
}

.link-arrow::after {
  content: "→";
  font-family: var(--font-mono);
  transition: transform 150ms var(--ease);
}

.link-arrow:hover::after { transform: translateX(4px); }

/* ---------- 7. 徽标 ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.375rem;
  padding: 0.25rem 0.625rem;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--fg-muted);
}

.badge--gold {
  color: var(--warm-gold);
  border-color: rgba(244, 201, 107, 0.42);
  background: rgba(244, 201, 107, 0.08);
}

.badge--celadon {
  color: var(--celadon-400);
  border-color: rgba(79, 209, 176, 0.42);
  background: rgba(79, 209, 176, 0.08);
}

.badge--alert {
  color: var(--alert-coral);
  border-color: rgba(255, 138, 122, 0.42);
  background: rgba(255, 138, 122, 0.08);
}

/* ---------- 8. 卡片 ---------- */
.card {
  position: relative;
  padding: clamp(1.25rem, 3vw, 1.75rem);
  border: 1px solid var(--line-soft);
  border-radius: var(--r-md);
  background: var(--abyss-700);
  box-shadow: var(--shadow-soft);
  transition: transform 180ms var(--ease), border-color 180ms var(--ease),
    background 180ms var(--ease);
}

.card:hover {
  transform: translateY(-2px);
  border-color: var(--abyss-500);
}

.card__num {
  display: block;
  margin-bottom: 0.75rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--signal-orange);
}

.card__title {
  margin-bottom: 0.4rem;
  font-family: var(--font-display);
  font-size: 1.125rem;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.card__text {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--fg-muted);
}

/* ---------- 9. 折叠组 ---------- */
.disclosure {
  overflow: hidden;
  border: 1px solid var(--line-soft);
  border-radius: var(--r-md);
  background: var(--abyss-700);
}

.disclosure + .disclosure { margin-top: 0.75rem; }

.disclosure__heading {
  margin: 0;
  font-size: var(--t-16);
  font-weight: 600;
  letter-spacing: 0;
}

.disclosure__trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  width: 100%;
  padding: 1rem 1.25rem;
  font-family: var(--font-body);
  font-size: var(--t-16);
  font-weight: 600;
  text-align: left;
  color: var(--ink-050);
  transition: background 150ms var(--ease);
}

.disclosure__trigger:hover { background: rgba(79, 209, 176, 0.07); }

.disclosure__icon {
  position: relative;
  flex: none;
  width: 18px;
  height: 18px;
}

.disclosure__icon::before,
.disclosure__icon::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 8px;
  height: 2px;
  background: var(--celadon-400);
  transition: transform 180ms var(--ease);
}

.disclosure__icon::after { transform: rotate(90deg); }

.disclosure__trigger[aria-expanded="true"] .disclosure__icon::after {
  transform: rotate(0deg);
}

.disclosure__panel {
  padding: 0 1.25rem 1.25rem;
  font-size: 0.9375rem;
  line-height: 1.75;
  color: var(--fg-muted);
  animation: panel-in 160ms var(--ease) both;
}

.disclosure__panel[hidden] { display: none; }

@keyframes panel-in {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: none; }
}

/* ---------- 10. 图片容器 ---------- */
.media {
  position: relative;
  margin: 0;
  overflow: hidden;
  border: 1px solid var(--line-soft);
  border-radius: var(--r-md);
  background: var(--abyss-700);
  aspect-ratio: 16 / 10;
}

.media--wide { aspect-ratio: 21 / 9; }
.media--square { aspect-ratio: 1 / 1; }

.media--diagram {
  background: linear-gradient(160deg, var(--abyss-700), var(--abyss-900));
}

.media--diagram::before {
  content: "";
  position: absolute;
  inset: 0;
  opacity: 0.26;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 32px 32px;
}

.media__img {
  position: relative;
  width: 100%;
  height: 100%;
  object-fit: cover;
  background: var(--abyss-500);
}

.media__caption {
  position: relative;
  margin-top: 0.625rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  letter-spacing: 0.08em;
  color: var(--fg-muted);
}

/* ---------- 11. 面包屑 ---------- */
.breadcrumb {
  padding-block: 1rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  letter-spacing: 0.08em;
}

.breadcrumb__list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}

.breadcrumb__item {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--fg-muted);
}

.breadcrumb__item:not(:last-child)::after {
  content: "/";
  color: var(--line);
}

.breadcrumb__item[aria-current="page"] { color: var(--ink-050); }

.breadcrumb__link {
  color: var(--fg-muted);
  text-decoration: none;
  transition: color 150ms var(--ease);
}

.breadcrumb__link:hover {
  color: var(--ink-050);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ---------- 12. 跳链 ---------- */
.skip-link {
  position: fixed;
  top: 8px;
  left: 50%;
  z-index: 400;
  padding: 0.625rem 1.125rem;
  border-radius: var(--r-pill);
  background: var(--signal-orange);
  color: var(--abyss-900);
  font-size: var(--t-14);
  font-weight: 700;
  text-decoration: none;
  white-space: nowrap;
  pointer-events: auto;
  transform: translate(-50%, -180%);
  transition: transform 180ms var(--ease);
  box-shadow: 0 14px 30px -16px rgba(0, 0, 0, 0.95);
}

.skip-link:focus-visible {
  transform: translate(-50%, 0);
  outline-color: var(--ink-050);
}

/* ---------- 13. 头部悬浮胶囊 ---------- */
.site-header {
  position: fixed;
  inset: 16px 0 auto;
  z-index: 120;
  display: flex;
  justify-content: center;
  padding-inline: 16px;
  pointer-events: none;
}

.site-header__bar {
  pointer-events: auto;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  width: min(var(--wrap), 100%);
  padding: 0.375rem;
  border: 1px solid var(--line-soft);
  border-radius: var(--r-pill);
  background: rgba(13, 42, 63, 0.88);
  box-shadow: 0 10px 30px -24px rgba(0, 0, 0, 0.9);
  -webkit-backdrop-filter: blur(18px) saturate(140%);
  backdrop-filter: blur(18px) saturate(140%);
  transition: background 180ms var(--ease), border-color 180ms var(--ease),
    box-shadow 180ms var(--ease);
}

.site-header[data-condensed] .site-header__bar {
  background: rgba(6, 24, 38, 0.96);
  border-color: var(--abyss-500);
  box-shadow: var(--shadow-soft);
}

/* 品牌胶囊 */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  flex: none;
  padding: 0.45rem 0.9rem 0.45rem 0.5rem;
  border-radius: var(--r-pill);
  background: rgba(23, 63, 92, 0.85);
  text-decoration: none;
  transition: background 150ms var(--ease);
}

.brand:hover { background: var(--abyss-500); }

.brand__mark {
  display: grid;
  place-items: center;
  flex: none;
  width: 28px;
  height: 28px;
  border-radius: 8px;
  background: var(--signal-orange);
  color: #08131F;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  box-shadow: 0 6px 18px -10px rgba(255, 107, 53, 0.95);
}

.brand__text {
  display: flex;
  flex-direction: column;
  line-height: 1.05;
}

.brand__name {
  font-family: var(--font-display);
  font-size: 0.9375rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--ink-050);
  white-space: nowrap;
}

.brand__version {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  color: var(--celadon-400);
}

/* 导航 */
.site-nav { margin-inline: auto; }

.site-nav__list {
  display: flex;
  align-items: center;
  gap: 0.125rem;
}

.site-nav__link {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding: 0.5rem 0.7rem;
  border-radius: var(--r-pill);
  font-size: var(--t-14);
  font-weight: 500;
  color: var(--steel-400);
  text-decoration: none;
  white-space: nowrap;
  transition: color 150ms var(--ease), background 150ms var(--ease);
}

.site-nav__link:hover {
  color: var(--ink-050);
  background: rgba(79, 209, 176, 0.12);
}

.site-nav__link[aria-current="page"] {
  background: var(--celadon-400);
  color: var(--abyss-900);
  font-weight: 700;
}

/* 动作区 */
.site-header__actions {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  flex: none;
}

/* 索引按钮（移动端） */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 0.45rem;
  padding: 0.45rem 0.8rem;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  background: rgba(23, 63, 92, 0.6);
  color: var(--ink-050);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  transition: border-color 150ms var(--ease), color 150ms var(--ease),
    background 150ms var(--ease);
}

.nav-toggle:hover {
  border-color: var(--celadon-400);
  color: var(--celadon-400);
}

.nav-toggle__bars {
  display: grid;
  gap: 4px;
  width: 16px;
}

.nav-toggle__bars i {
  display: block;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
  transition: transform 180ms var(--ease), opacity 180ms var(--ease);
}

.site-header[data-open] .nav-toggle__bars i:first-child {
  transform: translateY(3px) rotate(45deg);
}

.site-header[data-open] .nav-toggle__bars i:last-child {
  transform: translateY(-3px) rotate(-45deg);
}

/* ---------- 14. 页脚 ---------- */
.site-footer {
  position: relative;
  border-top: 1px solid var(--line);
  background: var(--abyss-800);
  color: var(--ink-050);
}

.site-footer::before {
  content: "";
  position: absolute;
  inset: 0 0 auto;
  height: 2px;
  background: linear-gradient(90deg, var(--signal-orange) 0 22%, rgba(255, 107, 53, 0) 22% 100%);
}

.site-footer__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) minmax(0, 0.9fr) minmax(0, 0.9fr);
  gap: clamp(1.75rem, 4vw, 3rem);
  padding-block: clamp(2.5rem, 6vw, 4.5rem) clamp(1.75rem, 4vw, 2.75rem);
}

.site-footer__lockup {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 3vw, var(--t-32));
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.site-footer__tagline {
  margin-top: 0.35rem;
  font-family: var(--font-serif);
  font-size: var(--t-16);
  color: var(--celadon-400);
}

.site-footer__meta {
  margin-top: 0.9rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  letter-spacing: 0.1em;
  color: var(--steel-400);
}

.footer-col__heading {
  margin-bottom: 1rem;
  font-family: var(--font-mono);
  font-size: var(--t-12);
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--steel-400);
}

.footer-col__list {
  display: grid;
  gap: 0.65rem;
}

.footer-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9375rem;
  color: var(--ink-050);
  text-decoration: none;
  transition: color 150ms var(--ease);
}

.footer-link::before {
  content: "";
  width: 0;
  height: 1px;
  background: var(--signal-orange);
  transition: width 180ms var(--ease);
}

.footer-link:hover { color: var(--signal-orange); }
.footer-link:hover::before { width: 12px; }

.site-footer__contact {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.6fr);
  gap: 1.5rem 2.5rem;
  padding-block: clamp(1.5rem, 4vw, 2.25rem);
  border-top: 1px solid var(--line);
}

.site-footer__note {
  max-width: 40ch;
  font-size: var(--t-14);
  line-height: 1.7;
  color: var(--steel-400);
}

.contact-list {
  display: grid;
  gap: 0.625rem;
}

.contact-list__row {
  display: grid;
  grid-template-columns: 4.25rem minmax(0, 1fr);
  gap: 0.75rem;
  align-items: baseline;
}

.contact-list__key {
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--celadon-400);
}

.contact-list__val {
  font-size: 0.9375rem;
  line-height: 1.6;
  color: var(--ink-050);
  overflow-wrap: anywhere;
}

.site-footer__legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.875rem 1.5rem;
  padding-block: 1.5rem;
  border-top: 1px solid var(--line);
  font-family: var(--font-mono);
  font-size: var(--t-12);
  letter-spacing: 0.06em;
  color: var(--steel-400);
}

.legal-links {
  display: flex;
  flex-wrap: wrap;
  gap: 1.25rem;
}

.legal-links .footer-link {
  font-family: var(--font-mono);
  font-size: var(--t-12);
  letter-spacing: 0.06em;
  color: var(--steel-400);
}

.legal-links .footer-link:hover { color: var(--signal-orange); }

.site-footer__icp,
.site-footer__copy { color: var(--steel-400); }

/* ---------- 15. 滚动显现 ---------- */
[data-reveal] {
  transition: opacity 480ms var(--ease), transform 480ms var(--ease);
}

html.js-reveal [data-reveal]:not(.is-revealed) {
  opacity: 0;
  transform: translateY(16px);
}

/* ---------- 16. 响应式 ---------- */
@media (max-width: 1120px) {
  .site-nav__link {
    padding: 0.45rem 0.55rem;
    font-size: 0.8125rem;
  }
  .site-header__actions .btn--ghost { display: none; }
}

@media (max-width: 980px) {
  .nav-toggle {
    display: inline-flex;
    order: 3;
  }

  .site-header__actions {
    order: 2;
    margin-left: auto;
  }

  .site-header__actions .btn--signal {
    padding: 0.45rem 0.7rem;
    font-size: 0.75rem;
  }

  .site-nav {
    position: fixed;
    left: 16px;
    right: 16px;
    top: calc(16px + var(--header-h) + 12px);
    max-height: calc(100vh - var(--header-h) - 60px);
    margin: 0;
    padding: 0.75rem;
    overflow-y: auto;
    border: 1px solid var(--line);
    border-radius: var(--r-lg);
    background: rgba(6, 24, 38, 0.97);
    box-shadow: var(--shadow-soft);
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translateY(-10px);
    transition: opacity 180ms var(--ease), transform 180ms var(--ease),
      visibility 180ms linear;
  }

  .site-header[data-open] .site-nav,
  .site-nav[data-open] {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    transform: none;
  }

  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
  }

  .site-nav__link {
    justify-content: space-between;
    padding: 0.9rem 1rem;
    border-radius: var(--r-md);
    font-size: var(--t-16);
  }

  .site-nav__link::after {
    content: "→";
    font-family: var(--font-mono);
    font-size: var(--t-14);
    color: var(--steel-400);
    transition: transform 150ms var(--ease);
  }

  .site-nav__link:hover::after { transform: translateX(3px); }

  .site-nav__link[aria-current="page"]::after { color: var(--abyss-900); }

  body.is-nav-open { overflow: hidden; }

  body.is-nav-open::before {
    content: "";
    position: fixed;
    inset: 0;
    z-index: 110;
    background: rgba(6, 24, 38, 0.74);
    -webkit-backdrop-filter: blur(3px);
    backdrop-filter: blur(3px);
  }

  .site-footer__contact { grid-template-columns: minmax(0, 1fr); }
}

@media (max-width: 820px) {
  .site-footer__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 2rem 1.5rem;
  }
  .site-footer__brand { grid-column: 1 / -1; }
}

@media (max-width: 560px) {
  .site-footer__grid { grid-template-columns: minmax(0, 1fr); }
  .contact-list__row { grid-template-columns: 3.75rem minmax(0, 1fr); }
  .site-footer__legal {
    flex-direction: column;
    align-items: flex-start;
  }
  .legal-links { gap: 1rem; }
}

/* ---------- 17. 降低动效 ---------- */
@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 !important;
    transform: none !important;
  }

  .site-header__bar { transition: background 120ms linear; }
}