/* ==========================================================================
   /assets/site.css — 共享外壳：重置、变量、排版、头部、页脚、通用组件
   ========================================================================== */

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

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

body { margin: 0; }

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

button { font: inherit; color: inherit; background: none; border: 0; }

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

ul, ol { margin: 0; padding: 0; }

a { color: inherit; }

/* ---------- 2. 设计令牌 ---------- */
:root {
  --c-deep: #0E2A4A;
  --c-night: #071A30;
  --c-gold: #D6A24A;
  --c-gold-soft: #F2D9A8;
  --c-cream: #F7F2E7;
  --c-paper: #FFFFFF;
  --c-line: #C9CFD6;
  --c-gray: #5A6472;
  --c-ink: #241F1C;
  --c-cyan: #35E0D0;
  --c-rust: #C4552F;

  --font-head: "HarmonyOS Sans SC", "PingFang SC", "Source Han Sans SC", "Noto Sans CJK SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --font-body: "Source Han Serif SC", "Noto Serif CJK SC", "Songti SC", "SimSun", Georgia, serif;
  --font-mono: "JetBrains Mono", "Sarasa Mono SC", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --rail-w: 84px;
  --pad: 24px;
  --maxw: 1180px;
  --radius: 3px;
}

/* ---------- 3. 基础排版 ---------- */
body {
  background-color: var(--c-cream);
  color: var(--c-ink);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.85;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4, h5 {
  font-family: var(--font-head);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--c-ink);
}

h1 { font-size: clamp(30px, 4vw, 44px); }
h2 { font-size: clamp(24px, 2.6vw, 34px); }
h3 { font-size: clamp(19px, 1.6vw, 26px); font-weight: 700; }
h4 { font-size: 20px; font-weight: 700; }
h5 { font-size: 17px; font-weight: 700; }

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

:focus-visible {
  outline: 2px solid var(--c-gold);
  outline-offset: 2px;
  box-shadow: 0 0 0 4px rgba(14, 42, 74, 0.28);
}

/* ---------- 4. 通用容器与工具类 ---------- */
.wrap {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding-left: var(--pad);
  padding-right: var(--pad);
}

.section { padding: 64px 0; }
.section--tight { padding: 36px 0; }
.section--cream { background-color: var(--c-cream); }
.section--paper { background-color: var(--c-paper); }
.section--night { background-color: var(--c-night); color: #DCE6F2; }
.section--night h1,
.section--night h2,
.section--night h3 { color: #F4F8FC; }

.section-head { max-width: 66ch; margin-bottom: 28px; }

.eyebrow {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--c-rust);
  margin-bottom: 10px;
}

.lead {
  font-family: var(--font-body);
  font-size: 19px;
  line-height: 1.8;
  color: var(--c-gray);
  max-width: 62ch;
  margin: 0;
}

.mono {
  font-family: var(--font-mono);
  font-size: 0.92em;
  letter-spacing: 0.04em;
  font-weight: 500;
}

.divider {
  height: 1px;
  border: 0;
  margin: 36px 0;
  background-color: var(--c-line);
}

.prose {
  max-width: 68ch;
  font-size: 17px;
  line-height: 1.85;
  color: var(--c-ink);
}
.prose p { margin: 0 0 1.05em; }
.prose h2 { margin: 1.6em 0 0.5em; font-size: 26px; }
.prose h3 { margin: 1.4em 0 0.4em; font-size: 20px; }
.prose ul, .prose ol { margin: 0 0 1.05em; padding-left: 1.4em; }
.prose li { margin: 0 0 0.4em; }
.prose strong { font-weight: 700; }
.prose a {
  color: var(--c-deep);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: var(--c-gold);
}

/* ---------- 5. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-head);
  font-size: 15px;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: 0.01em;
  padding: 12px 20px;
  border: 1px solid transparent;
  border-radius: 2px;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.btn--gold { background-color: var(--c-gold); color: #1B1408; border-color: var(--c-gold); }
.btn--gold:hover { background-color: var(--c-gold-soft); border-color: var(--c-gold-soft); }
.btn--ghost { background-color: transparent; color: var(--c-deep); border-color: var(--c-line); }
.btn--ghost:hover { border-color: var(--c-gold); background-color: rgba(214, 162, 74, 0.12); }
.btn--sm { font-size: 12.5px; padding: 8px 12px; }
.btn--block { width: 100%; }

/* ---------- 6. 卡片 ---------- */
.card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 22px;
  background-color: var(--c-paper);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, border-color 0.2s ease;
}
a.card:hover { transform: translateY(-4px); border-color: var(--c-gold); }
.card__eyebrow {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--c-rust);
}
.card__title {
  font-family: var(--font-head);
  font-size: 20px;
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--c-ink);
}
.card__body { font-size: 15.5px; line-height: 1.75; color: var(--c-gray); }
.card__meta {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--c-gray);
  margin-top: auto;
}

/* ---------- 7. 栅格 ---------- */
.grid { display: grid; gap: 20px; }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

/* ---------- 8. 章节带 / 面包屑 / 标签 / 时间轴 ---------- */
.chapter-band {
  position: relative;
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding-left: 18px;
  margin: 0 0 18px;
}
.chapter-band::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.12em;
  bottom: 0.12em;
  width: 6px;
  border-radius: 1px;
  background-color: var(--c-gold);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 0.24s cubic-bezier(0.2, 0.7, 0.3, 1);
}
.chapter-band.is-visible::before,
.is-visible > .chapter-band::before { transform: scaleX(1); }
.chapter-band__num {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.16em;
  color: var(--c-rust);
}
.chapter-band__title {
  font-family: var(--font-head);
  font-size: clamp(22px, 2.4vw, 26px);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.2;
  color: var(--c-ink);
}
.section--night .chapter-band__title { color: #F4F8FC; }
.section--night .chapter-band__num { color: var(--c-gold-soft); }

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  list-style: none;
  margin: 0 0 20px;
  padding: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--c-gray);
}
.breadcrumb__item { display: inline-flex; align-items: center; gap: 8px; }
.breadcrumb__item + .breadcrumb__item::before { content: "/"; color: var(--c-line); }
.breadcrumb__item a { color: var(--c-gray); text-decoration: none; }
.breadcrumb__item a:hover { color: var(--c-rust); text-decoration: underline; text-underline-offset: 3px; }
.breadcrumb__item[aria-current="page"] { color: var(--c-ink); }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.1em;
  padding: 3px 9px;
  border: 1px solid var(--c-line);
  border-radius: 999px;
  background-color: var(--c-paper);
  color: var(--c-gray);
}
.tag--gold { border-color: rgba(214, 162, 74, 0.6); background-color: var(--c-gold-soft); color: #6B4A12; }
.tag--cyan { border-color: rgba(53, 224, 208, 0.6); background-color: rgba(53, 224, 208, 0.14); color: #0B5C56; }
.tag--rust { border-color: rgba(196, 85, 47, 0.5); background-color: rgba(196, 85, 47, 0.1); color: var(--c-rust); }

.timeline { list-style: none; margin: 0; padding: 0; position: relative; }
.timeline::before {
  content: "";
  position: absolute;
  left: 5px;
  top: 10px;
  bottom: 10px;
  width: 1px;
  background-color: var(--c-line);
}
.timeline__item { position: relative; padding: 0 0 28px 28px; }
.timeline__item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 7px;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  background-color: var(--c-paper);
  border: 2px solid var(--c-gold);
  transition: background-color 0.2s ease, border-color 0.2s ease;
}
.timeline__item.is-current::before { background-color: var(--c-cyan); border-color: var(--c-cyan); }
.timeline__label {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--c-rust);
  margin-bottom: 6px;
}

/* ---------- 9. 提示条 / 数据块 / 表格 ---------- */
.note-band {
  border-left: 4px solid var(--c-gold);
  background-color: var(--c-paper);
  padding: 18px 22px;
  font-size: 15.5px;
  line-height: 1.8;
  color: var(--c-gray);
  border-radius: 0 var(--radius) var(--radius) 0;
}
.note-band strong { color: var(--c-ink); font-weight: 700; }

.stat { display: flex; flex-direction: column; gap: 4px; }
.stat__value {
  font-family: var(--font-mono);
  font-size: 26px;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.01em;
  color: var(--c-deep);
}
.stat__label { font-size: 13.5px; line-height: 1.6; color: var(--c-gray); }

.table-wrap {
  width: 100%;
  overflow-x: auto;
  background-color: var(--c-paper);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
}
table.spec-table { width: 100%; border-collapse: collapse; font-size: 15px; line-height: 1.7; }
.spec-table th,
.spec-table td {
  padding: 12px 16px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--c-line);
}
.spec-table th {
  font-family: var(--font-head);
  font-size: 13.5px;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--c-deep);
  background-color: #F1F4F8;
  white-space: nowrap;
}
.spec-table tr:last-child td { border-bottom: 0; }

/* ---------- 10. 图片容器（共享基础规则，供页面阶段放图） ---------- */
.media-frame {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  background-color: var(--c-deep);
  background-image: linear-gradient(150deg, #12345A 0%, #0E2A4A 45%, #071A30 100%);
}
.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--4x3 { aspect-ratio: 4 / 3; }
.media-frame--square { aspect-ratio: 1 / 1; }
.media-frame--tall { aspect-ratio: 3 / 4; }
.media-frame img { width: 100%; height: 100%; object-fit: cover; display: block; }
.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  box-shadow: inset 0 0 46px rgba(7, 26, 48, 0.6);
  background-image: repeating-linear-gradient(0deg, rgba(255, 255, 255, 0.035) 0 1px, transparent 1px 5px);
}
.media-frame__inner {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 16px;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: rgba(242, 217, 168, 0.55);
}

/* ---------- 11. 跳过链接 ---------- */
.skip-link {
  position: fixed;
  top: -120px;
  left: 12px;
  z-index: 90;
  padding: 10px 16px;
  background-color: var(--c-gold);
  color: #1B1408;
  font-family: var(--font-head);
  font-size: 14px;
  font-weight: 700;
  text-decoration: none;
  border-radius: 2px;
  transition: top 0.18s ease;
}
.skip-link:focus { top: 12px; }

/* ---------- 12. 顶部滚动进度条 ---------- */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  z-index: 80;
  pointer-events: none;
  background-color: rgba(7, 26, 48, 0.28);
}
.scroll-progress__bar {
  display: block;
  height: 100%;
  width: 0;
  background-image: linear-gradient(90deg, #C4552F 0%, #D6A24A 45%, #F2D9A8 100%);
  transition: width 0.12s linear;
}

/* ---------- 13. 框架式导航轨道 ---------- */
.site-rail {
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  width: var(--rail-w);
  z-index: 70;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
  padding: 20px 8px 18px;
  overflow-y: auto;
  overflow-x: hidden;
  color: #DCE6F2;
  background-color: var(--c-deep);
  background-image: repeating-linear-gradient(0deg, rgba(255, 255, 255, 0.035) 0 1px, transparent 1px 4px);
  border-right: 1px solid rgba(214, 162, 74, 0.32);
}

.brand-mark {
  flex: none;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  text-align: center;
  text-decoration: none;
  color: inherit;
}
.brand-mark__glyph {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border: 1px solid var(--c-gold);
  border-radius: 2px;
  background-image: linear-gradient(180deg, rgba(214, 162, 74, 0.24), rgba(214, 162, 74, 0.04));
  color: var(--c-gold);
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.06em;
}
.brand-mark__text { display: flex; flex-direction: column; gap: 2px; width: 100%; }
.brand-mark__name {
  font-family: var(--font-head);
  font-size: 8px;
  font-weight: 700;
  letter-spacing: 0.1em;
  line-height: 1.2;
  color: var(--c-gold-soft);
}
.brand-mark__sub {
  font-family: var(--font-head);
  font-size: 9px;
  line-height: 1.35;
  letter-spacing: 0.02em;
  color: #94A9C0;
  word-break: break-word;
}

.rail-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 7px 10px;
  border: 1px solid rgba(214, 162, 74, 0.45);
  border-radius: 2px;
  background-color: transparent;
  color: var(--c-gold-soft);
  font-family: var(--font-head);
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
}
.rail-toggle__bars { display: flex; flex-direction: column; gap: 3px; width: 16px; }
.rail-toggle__bars span {
  display: block;
  height: 2px;
  border-radius: 1px;
  background-color: currentColor;
  transition: transform 0.2s ease, opacity 0.2s ease;
}
.rail-toggle[aria-expanded="true"] .rail-toggle__bars span:nth-child(1) { transform: translateY(5px) rotate(45deg); }
.rail-toggle[aria-expanded="true"] .rail-toggle__bars span:nth-child(2) { opacity: 0; }
.rail-toggle[aria-expanded="true"] .rail-toggle__bars span:nth-child(3) { transform: translateY(-5px) rotate(-45deg); }
.rail-toggle__label { font-family: var(--font-head); font-size: 13px; font-weight: 700; letter-spacing: 0.06em; }

.rail-nav {
  flex: 1 1 auto;
  min-height: 0;
  width: 100%;
  display: flex;
  align-items: center;
}
.rail-nav__list { list-style: none; width: 100%; display: flex; flex-direction: column; gap: 3px; }
.rail-nav__link {
  position: relative;
  display: block;
  padding: 8px 2px;
  text-align: center;
  text-decoration: none;
  color: #B9C9DA;
  border-radius: 2px;
  transition: color 0.18s ease, background-color 0.18s ease;
}
.rail-nav__link:hover { color: var(--c-gold-soft); background-color: rgba(214, 162, 74, 0.14); }
.rail-nav__link[aria-current="page"] { color: #FFFFFF; background-color: rgba(214, 162, 74, 0.2); }
.rail-nav__link[aria-current="page"]::before {
  content: "";
  position: absolute;
  left: -8px;
  top: 6px;
  bottom: 6px;
  width: 3px;
  border-radius: 0 2px 2px 0;
  background-color: var(--c-gold);
}
.rail-nav__idx {
  display: block;
  font-family: var(--font-mono);
  font-size: 9px;
  font-weight: 500;
  line-height: 1.2;
  letter-spacing: 0.1em;
  color: rgba(214, 162, 74, 0.72);
}
.rail-nav__link[aria-current="page"] .rail-nav__idx { color: var(--c-gold); }
.rail-nav__label {
  display: block;
  font-family: var(--font-head);
  font-size: 11px;
  font-weight: 500;
  line-height: 1.35;
  letter-spacing: 0.02em;
}

.rail-actions { flex: none; width: 100%; display: flex; flex-direction: column; gap: 8px; }
.rail-action {
  display: block;
  width: 100%;
  padding: 8px 3px;
  text-align: center;
  text-decoration: none;
  font-family: var(--font-head);
  font-size: 10.5px;
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: 0.02em;
  border: 1px solid transparent;
  border-radius: 2px;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.rail-action--solid { background-color: var(--c-gold); color: #1B1408; }
.rail-action--solid:hover { background-color: var(--c-gold-soft); }
.rail-action--quiet { color: var(--c-gold-soft); border-color: rgba(214, 162, 74, 0.5); }
.rail-action--quiet:hover { background-color: rgba(214, 162, 74, 0.16); }

/* ---------- 14. 页脚 ---------- */
.site-foot {
  background-color: var(--c-night);
  background-image: repeating-linear-gradient(0deg, rgba(255, 255, 255, 0.025) 0 1px, transparent 1px 5px);
  color: #C3D2E2;
  border-top: 1px solid rgba(214, 162, 74, 0.4);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.8;
}
.foot-top {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.9fr);
  gap: 44px;
  padding-top: 52px;
  padding-bottom: 36px;
}
.foot-brand { display: flex; flex-direction: column; gap: 12px; }
.foot-brand__mark {
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  border: 1px solid var(--c-gold);
  border-radius: 2px;
  background-image: linear-gradient(180deg, rgba(214, 162, 74, 0.24), rgba(214, 162, 74, 0.04));
  color: var(--c-gold);
  font-family: var(--font-mono);
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.06em;
}
.foot-brand__name {
  font-family: var(--font-head);
  font-size: 17px;
  font-weight: 700;
  line-height: 1.4;
  letter-spacing: 0.01em;
  color: #F2F6FB;
}
.foot-brand__desc { max-width: 34ch; font-size: 14px; line-height: 1.8; color: #93A6BC; }

.foot-cols { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 28px; }
.foot-col { display: flex; flex-direction: column; gap: 12px; }
.foot-col__title {
  font-family: var(--font-head);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.14em;
  color: var(--c-gold);
  text-transform: uppercase;
}
.foot-col__list { list-style: none; display: flex; flex-direction: column; gap: 9px; }
.foot-col__list a {
  font-size: 14.5px;
  color: #BCCBDD;
  text-decoration: none;
  transition: color 0.16s ease;
}
.foot-col__list a:hover { color: var(--c-gold-soft); text-decoration: underline; text-underline-offset: 3px; }

.foot-contact {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding-top: 24px;
  padding-bottom: 24px;
  border-top: 1px solid rgba(214, 162, 74, 0.22);
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.9;
  letter-spacing: 0.01em;
  color: #A9BBD0;
}
.foot-contact__line { word-break: break-word; }
.foot-contact__note { font-family: var(--font-body); font-size: 12.5px; color: #7D90A6; }

.foot-base {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding-top: 18px;
  padding-bottom: 28px;
  border-top: 1px solid rgba(214, 162, 74, 0.22);
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  color: #7D90A6;
}

/* ---------- 15. 返回顶部 ---------- */
.backtop {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 65;
  width: 46px;
  height: 46px;
  display: grid;
  place-items: center;
  border: 1px solid rgba(214, 162, 74, 0.5);
  border-radius: 2px;
  background-color: var(--c-deep);
  color: var(--c-gold-soft);
  font-family: var(--font-mono);
  font-size: 16px;
  line-height: 1;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: opacity 0.24s ease, transform 0.24s ease, visibility 0.24s ease, background-color 0.18s ease, color 0.18s ease;
}
.backtop.is-visible { opacity: 1; visibility: visible; transform: none; }
.backtop:hover { background-color: var(--c-gold); color: #1B1408; border-color: var(--c-gold); }

/* ---------- 16. 进入视口显现协议 ---------- */
html.has-js [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
html.has-js [data-reveal].is-visible { opacity: 1; transform: none; }

/* ---------- 17. 断点：桌面端内容让位导航轨道 ---------- */
@media (min-width: 960px) {
  body { padding-left: var(--rail-w); }
  .scroll-progress { left: var(--rail-w); }
  .skip-link { left: calc(var(--rail-w) + 12px); }
  #main-content { scroll-margin-top: 32px; }
}

/* ---------- 18. 断点：平板 / 手机 —— 导航折叠为顶部胶囊条 ---------- */
@media (max-width: 959px) {
  body { padding-top: 62px; }

  .site-rail {
    top: 0;
    left: 0;
    right: 0;
    bottom: auto;
    width: 100%;
    flex-direction: row;
    flex-wrap: wrap;
    align-items: center;
    gap: 10px;
    padding: 10px 16px;
    border-right: 0;
    border-bottom: 1px solid rgba(214, 162, 74, 0.32);
    overflow-x: hidden;
    overflow-y: auto;
    max-height: 100vh;
  }

  .brand-mark { flex-direction: row; align-items: center; gap: 10px; text-align: left; }
  .brand-mark__glyph { width: 34px; height: 34px; font-size: 12px; }
  .brand-mark__name { font-size: 11px; letter-spacing: 0.12em; }
  .brand-mark__sub { font-size: 11px; color: #9FB2C7; }

  .rail-toggle { display: inline-flex; margin-left: auto; flex: none; }

  .rail-nav {
    order: 3;
    flex: none;
    display: none;
    width: 100%;
    margin-top: 4px;
    padding: 6px 0 10px;
    border-top: 1px solid rgba(214, 162, 74, 0.22);
  }
  .site-rail[data-open] .rail-nav,
  .rail-nav[data-open] { display: block; }

  .rail-nav__list { gap: 0; }
  .rail-nav__link {
    display: flex;
    align-items: baseline;
    gap: 10px;
    padding: 12px 4px;
    text-align: left;
    border-left: 3px solid transparent;
    border-bottom: 1px solid rgba(214, 162, 74, 0.14);
    border-radius: 0;
  }
  .rail-nav__link[aria-current="page"] { border-left-color: var(--c-gold); }
  .rail-nav__link[aria-current="page"]::before { display: none; }
  .rail-nav__idx { display: inline; font-size: 11px; }
  .rail-nav__label { font-size: 15px; font-weight: 600; }

  .rail-actions { order: 4; display: none; flex-direction: row; gap: 10px; width: 100%; padding-bottom: 12px; }
  .site-rail[data-open] .rail-actions { display: flex; }
  .rail-action { flex: 1 1 0; font-size: 13px; padding: 10px 6px; }

  .backtop { right: 14px; bottom: 14px; width: 42px; height: 42px; }
  #main-content { scroll-margin-top: 84px; }
}

/* ---------- 19. 断点：页脚与栅格 ---------- */
@media (max-width: 1100px) {
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 900px) {
  .foot-top { grid-template-columns: minmax(0, 1fr); gap: 32px; padding-top: 40px; }
  .foot-cols { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 24px; }
}

@media (max-width: 640px) {
  h1 { font-size: 29px; }
  h2 { font-size: 23px; }
  h3 { font-size: 19px; }
  .lead { font-size: 17px; }
  .section { padding: 44px 0; }
  .grid--2, .grid--3, .grid--4 { grid-template-columns: minmax(0, 1fr); }
  .card { padding: 18px; }
}

@media (max-width: 520px) {
  .foot-cols { grid-template-columns: minmax(0, 1fr); }
}

/* ---------- 20. 降低动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    transition-delay: 0ms !important;
  }
  html.has-js [data-reveal] { opacity: 1 !important; transform: none !important; }
  .chapter-band::before { transform: scaleX(1) !important; }
  .scroll-progress__bar { transition: none !important; }
}