/* =========================================================
   小鸟综合体育 · /assets/site.css
   全站共享：reset / 变量 / 排版 / 头部 / 页脚 / 通用组件
   ========================================================= */

/* ---------- 1. reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body, h1, h2, h3, h4, p, ul, ol, li, figure, blockquote, dl, dd { margin: 0; }
ul, ol { padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; }
img, svg, video { display: block; max-width: 100%; }
table { border-collapse: collapse; width: 100%; }

/* ---------- 2. 变量 ---------- */
:root {
  --siren: #FFC61A;
  --pitch: #1F7A4D;
  --night: #0E1B2E;
  --night-2: #182B45;
  --warm: #F6F3EC;
  --paper: #E7E1D6;
  --flare: #FF6B2C;
  --ink: #101418;
  --cool: #6B7480;
  --mint: #DCE9E1;

  --rail-w: 244px;
  --bar-h: 62px;
  --line: 4px;

  --font-display: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: system-ui, -apple-system, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  --r-lg: 26px;
  --r-md: 16px;
  --r-sm: 10px;
  --gap: clamp(16px, 3vw, 32px);
  --shadow-card: 0 1px 0 var(--paper), 0 16px 34px -24px rgba(16, 20, 24, 0.55);
}

/* ---------- 3. 基础排版 ---------- */
html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--bar-h) + 24px);
}
body {
  background: var(--warm);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.75;
  padding-top: calc(var(--bar-h) + var(--line));
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.05;
  letter-spacing: -0.01em;
}
h1 { font-size: clamp(32px, 6.4vw, 72px); }
h2 { font-size: clamp(24px, 3.6vw, 40px); }
h3 { font-size: clamp(19px, 2.2vw, 25px); }
h4 { font-size: 18px; line-height: 1.3; }
p { max-width: 38em; }
strong { font-weight: 700; }

.mono, [data-year] {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.08em;
}
.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--pitch);
}
.lede {
  font-size: clamp(17px, 1.5vw, 19px);
  line-height: 1.8;
  color: #2b323a;
  max-width: 36em;
}
.note {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.06em;
  color: var(--cool);
}

/* ---------- 4. 焦点与跳转 ---------- */
:where(a, button, summary, [tabindex]):focus-visible {
  outline: 3px solid var(--siren);
  outline-offset: 2px;
  border-radius: 4px;
}
.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 120;
  transform: translateY(-180%);
  padding: 10px 18px;
  background: var(--siren);
  color: var(--ink);
  border-radius: var(--r-sm);
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.08em;
  transition: transform 0.18s ease;
}
.skip-link:focus { transform: none; }
#main-content {
  display: block;
  scroll-margin-top: calc(var(--bar-h) + 20px);
}
#main-content:focus-visible { outline: 3px solid var(--siren); outline-offset: -3px; }

/* ---------- 5. 滚动哨声线 ---------- */
.scroll-meter {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--line);
  z-index: 110;
  background: rgba(107, 116, 128, 0.28);
  pointer-events: none;
}
.scroll-meter-fill {
  display: block;
  width: 100%;
  height: 100%;
  transform: scaleX(0);
  transform-origin: left center;
  background: linear-gradient(90deg, var(--pitch) 0%, var(--siren) 68%, var(--flare) 100%);
  transition: transform 0.12s linear;
}

/* ---------- 6. 头部 / 框架式导航 ---------- */
.site-header {
  position: fixed;
  z-index: 90;
  top: 0; left: 0; right: 0;
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: calc(var(--bar-h) + var(--line));
  padding: var(--line) 16px 0;
  background: linear-gradient(180deg, #12213a 0%, var(--night) 70%);
  color: var(--warm);
  border-bottom: 1px solid rgba(31, 122, 77, 0.75);
  box-shadow: 0 10px 28px -22px rgba(16, 20, 24, 0.9);
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
  flex: 0 1 auto;
}
.brand-mark {
  width: 34px;
  height: 34px;
  flex: 0 0 auto;
  color: var(--siren);
}
.brand-glyph { width: 100%; height: 100%; }
.brand-glyph .gl-hole { fill: var(--night); }
.brand-type { display: flex; flex-direction: column; min-width: 0; }
.brand-name {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 17px;
  letter-spacing: 0.01em;
  white-space: nowrap;
}
.brand-tagline {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: rgba(246, 243, 236, 0.62);
  white-space: nowrap;
}

.nav-toggle {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  margin-left: auto;
  padding: 9px 13px;
  border: 1px solid rgba(31, 122, 77, 0.9);
  border-radius: var(--r-sm);
  background: var(--night-2);
  color: var(--warm);
  cursor: pointer;
  transition: background-color 0.16s ease, border-color 0.16s ease;
}
.nav-toggle:hover { border-color: var(--siren); }
.nav-toggle-icon { display: grid; gap: 4px; width: 18px; }
.nav-toggle-icon span {
  display: block;
  height: 2px;
  border-radius: 2px;
  background: var(--siren);
  transition: transform 0.18s ease, opacity 0.18s ease;
}
.nav-toggle-icon span:nth-child(2) { width: 68%; }
.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle-icon span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }
.nav-toggle-text {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
}

.site-nav {
  position: absolute;
  top: 100%; left: 0; right: 0;
  display: flex;
  flex-direction: column;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  visibility: hidden;
  background: linear-gradient(180deg, var(--night) 0%, #0a1524 100%);
  border-bottom: 1px solid rgba(31, 122, 77, 0.75);
  transition: max-height 0.28s ease, opacity 0.2s ease, visibility 0.28s;
}
.site-nav[data-open] {
  max-height: calc(100vh - var(--bar-h));
  overflow-y: auto;
  opacity: 1;
  visibility: visible;
  padding-bottom: 20px;
}
.nav-caption {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 18px 16px 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: rgba(246, 243, 236, 0.55);
}
.nav-caption::before {
  content: "";
  width: 24px;
  height: 2px;
  border-radius: 2px;
  background: var(--siren);
  flex: 0 0 auto;
}
.nav-list { display: flex; flex-direction: column; }
.nav-link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  border-left: 3px solid transparent;
  color: rgba(246, 243, 236, 0.86);
  transition: background-color 0.16s ease, color 0.16s ease, border-color 0.16s ease;
}
.nav-link:hover { background: var(--night-2); color: #fff; }
.nav-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 11px;
  letter-spacing: 0.08em;
  color: rgba(255, 198, 26, 0.72);
}
.nav-text { font-size: 15.5px; }
.nav-link[aria-current="page"] {
  background: rgba(31, 122, 77, 0.3);
  border-left-color: var(--siren);
  color: #fff;
}
.nav-link[aria-current="page"] .nav-num { color: var(--siren); }

.nav-tail {
  display: grid;
  gap: 14px;
  margin-top: 18px;
  padding: 0 16px;
}
.quick-list { display: flex; flex-wrap: wrap; gap: 8px; }
.quick-link {
  display: inline-block;
  padding: 5px 11px;
  border: 1px solid rgba(31, 122, 77, 0.75);
  border-radius: 999px;
  background: rgba(24, 43, 69, 0.75);
  color: rgba(246, 243, 236, 0.82);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  transition: border-color 0.16s ease, color 0.16s ease;
}
.quick-link:hover { border-color: var(--siren); color: #fff; }

/* ---------- 7. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 20px;
  border: 1px solid transparent;
  border-radius: 999px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 15px;
  letter-spacing: 0.02em;
  cursor: pointer;
  transition: transform 0.16s ease, background-color 0.16s ease, border-color 0.16s ease, color 0.16s ease;
}
.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }
.btn-siren { background: var(--siren); color: var(--ink); }
.btn-siren:hover { background: #ffd451; }
.btn-pitch { background: var(--pitch); color: #fff; }
.btn-pitch:hover { background: #268f5b; }
.btn-ghost { background: transparent; border-color: var(--pitch); color: var(--pitch); }
.btn-ghost:hover { background: var(--mint); }
.btn-flare { background: var(--flare); color: #fff; }
.btn-flare:hover { background: #ff7f47; }
.btn-block { width: 100%; }

/* ---------- 8. 容器与网格 ---------- */
.wrap {
  width: 100%;
  max-width: 1240px;
  margin-inline: auto;
  padding-inline: clamp(16px, 4vw, 48px);
}
.wrap--wide { max-width: 1440px; }
.grid { display: grid; gap: var(--gap); }
.grid-12 { grid-template-columns: repeat(12, minmax(0, 1fr)); }
.col-3 { grid-column: span 3; }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-6 { grid-column: span 6; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-9 { grid-column: span 9; }
.col-12 { grid-column: span 12; }
.split {
  display: grid;
  gap: var(--gap);
  grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr);
  align-items: start;
}

/* ---------- 9. 章节与刻度尺 ---------- */
.section { position: relative; padding-block: clamp(42px, 7vw, 86px); }
.section--tight { padding-block: clamp(26px, 4vw, 46px); }
.section--night { background: var(--night); color: var(--warm); }
.section--paper { background: var(--paper); }
.section--mint { background: var(--mint); }
.section--lines::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(90deg, rgba(16, 20, 24, 0.055) 0 1px, transparent 1px 96px);
  pointer-events: none;
}
.section-head { display: grid; gap: 10px; margin-bottom: clamp(20px, 3vw, 36px); }
.section-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--pitch);
}
.section--night .section-num { color: var(--siren); }
.ruler {
  height: 16px;
  margin-block: clamp(18px, 3vw, 34px);
  border-top: 1px solid rgba(16, 20, 24, 0.14);
  background-image: repeating-linear-gradient(90deg, rgba(31, 122, 77, 0.45) 0 1px, transparent 1px 32px);
  background-repeat: repeat-x;
  background-size: auto 7px;
}
.section--night .ruler {
  border-top-color: rgba(246, 243, 236, 0.18);
  background-image: repeating-linear-gradient(90deg, rgba(255, 198, 26, 0.45) 0 1px, transparent 1px 32px);
}
.whistle-line {
  height: 6px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--pitch) 0 20%, var(--siren) 20% 42%, var(--night-2) 42% 100%);
}
.whistle-line--soft { opacity: 0.45; }

/* ---------- 10. 档案卡 / 标签 / 步骤 ---------- */
.file-card {
  position: relative;
  background: #fff;
  border: 1px solid var(--paper);
  border-radius: var(--r-md) var(--r-lg) var(--r-md) var(--r-md);
  padding: clamp(18px, 2.4vw, 26px);
  box-shadow: var(--shadow-card);
  transition: transform 0.16s ease, box-shadow 0.16s ease;
}
.file-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 22px 42px -28px rgba(16, 20, 24, 0.65);
}
.file-card__head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--cool);
}
.file-card__title { font-size: clamp(19px, 2.2vw, 24px); margin-bottom: 8px; }
.file-card__body { font-size: 16px; line-height: 1.75; color: #2b323a; max-width: 36em; }
.file-card--mint { background: var(--mint); border-color: rgba(31, 122, 77, 0.3); }
.file-card--night { background: var(--night); border-color: rgba(31, 122, 77, 0.55); color: var(--warm); }
.file-card--night .file-card__head { color: rgba(246, 243, 236, 0.6); }
.file-card--night .file-card__body { color: rgba(246, 243, 236, 0.8); }

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border: 1px solid rgba(31, 122, 77, 0.35);
  border-radius: 999px;
  background: var(--mint);
  color: #14563a;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
}
.tag--flare { background: rgba(255, 107, 44, 0.14); color: #b73f0d; border-color: rgba(255, 107, 44, 0.5); }
.tag--siren { background: rgba(255, 198, 26, 0.22); color: #7a5900; border-color: rgba(255, 198, 26, 0.7); }
.tag--night { background: var(--night-2); color: var(--warm); border-color: rgba(31, 122, 77, 0.7); }

.steps { display: grid; gap: 12px; }
.step {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 12px;
  align-items: start;
  padding: 12px 15px;
  border-radius: var(--r-md);
  background: var(--paper);
}
.section--night .step { background: var(--night-2); }
.step__num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--pitch);
  padding-top: 4px;
}
.section--night .step__num { color: var(--siren); }
.step__text { font-size: 15.5px; }

/* ---------- 11. 密集索引 ---------- */
.index-list { display: grid; border-top: 1px solid rgba(16, 20, 24, 0.14); }
.index-row {
  display: grid;
  grid-template-columns: 76px minmax(0, 1fr) auto;
  gap: 8px 14px;
  align-items: baseline;
  padding: 14px 8px;
  border-bottom: 1px solid rgba(16, 20, 24, 0.14);
  transition: background-color 0.16s ease;
}
.index-row:hover,
.index-row:focus-within { background: rgba(220, 233, 225, 0.6); }
.index-row__key {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--pitch);
}
.index-row__title { font-size: 16.5px; font-weight: 600; line-height: 1.5; }
.index-row__meta {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--cool);
}
.index-row__summary {
  grid-column: 2 / -1;
  max-height: 0;
  margin-top: 0;
  overflow: hidden;
  opacity: 0;
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--cool);
  transition: max-height 0.22s ease, opacity 0.22s ease, margin-top 0.22s ease;
}
.index-row:hover .index-row__summary,
.index-row:focus-within .index-row__summary { max-height: 6em; margin-top: 6px; opacity: 1; }
.section--night .index-list,
.section--night .index-row { border-color: rgba(246, 243, 236, 0.18); }
.section--night .index-row:hover,
.section--night .index-row:focus-within { background: rgba(31, 122, 77, 0.22); }
.section--night .index-row__key { color: var(--siren); }

/* ---------- 12. 章节跟随目录 ---------- */
.toc {
  position: sticky;
  top: calc(var(--bar-h) + 24px);
  display: grid;
  gap: 2px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
}
.toc__title {
  margin-bottom: 8px;
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--cool);
}
.toc a {
  display: block;
  padding: 7px 11px;
  border-left: 2px solid transparent;
  color: var(--cool);
  transition: color 0.16s ease, background-color 0.16s ease, border-color 0.16s ease;
}
.toc a:hover { color: var(--pitch); }
.toc a[aria-current="true"] {
  color: var(--ink);
  border-left-color: var(--siren);
  background: rgba(255, 198, 26, 0.16);
}

/* ---------- 13. 文本与数据块 ---------- */
.stat-grid { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); }
.stat { display: grid; gap: 4px; padding: 14px 16px; background: var(--paper); border-radius: var(--r-md); }
.stat__value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(22px, 3vw, 30px);
  letter-spacing: -0.02em;
  color: var(--pitch);
}
.stat__label { font-size: 13px; color: var(--cool); }
.section--night .stat { background: var(--night-2); }
.section--night .stat__value { color: var(--siren); }
.section--night .stat__label { color: rgba(246, 243, 236, 0.65); }
.panel {
  background: #fff;
  border: 1px solid var(--paper);
  border-radius: var(--r-lg);
  padding: clamp(18px, 2.6vw, 30px);
}
.panel--night { background: var(--night); color: var(--warm); border-color: rgba(31, 122, 77, 0.6); }
.link-more {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding-bottom: 2px;
  border-bottom: 1px solid currentColor;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.08em;
  color: var(--pitch);
  transition: color 0.16s ease;
}
.link-more::after { content: "→"; }
.link-more:hover { color: var(--flare); }

/* ---------- 14. 折叠面板 ---------- */
.fold {
  border: 1px solid var(--paper);
  border-radius: var(--r-md);
  background: #fff;
  overflow: hidden;
}
.fold + .fold { margin-top: 10px; }
.fold > summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 18px;
  cursor: pointer;
  font-weight: 600;
  list-style: none;
  transition: background-color 0.16s ease;
}
.fold > summary::-webkit-details-marker { display: none; }
.fold > summary:hover { background: rgba(220, 233, 225, 0.6); }
.fold > summary::after {
  content: "+";
  font-family: var(--font-mono);
  color: var(--pitch);
  flex: 0 0 auto;
}
.fold[open] > summary::after { content: "–"; }
.fold__body { padding: 0 18px 18px; font-size: 16px; color: #2b323a; }

/* ---------- 15. 面包屑 ---------- */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--cool);
}
.crumbs li { display: flex; align-items: center; gap: 8px; }
.crumbs li + li::before { content: "/"; color: rgba(107, 116, 128, 0.6); }
.crumbs a:hover { color: var(--pitch); }
.crumbs [aria-current="page"] { color: var(--ink); }

/* ---------- 16. 图文容器 ---------- */
.media {
  position: relative;
  overflow: hidden;
  aspect-ratio: 16 / 9;
  border: 1px solid rgba(31, 122, 77, 0.4);
  border-radius: var(--r-lg) var(--r-md) var(--r-lg) var(--r-md);
  background: linear-gradient(135deg, var(--night-2) 0%, var(--night) 65%);
}
.media > img,
.media > video,
.media > svg { width: 100%; height: 100%; object-fit: cover; }
.media--wide { aspect-ratio: 21 / 9; }
.media--tall { aspect-ratio: 4 / 5; }
.media--portrait { aspect-ratio: 3 / 4; }
.media--square { aspect-ratio: 1 / 1; }
.media__caption {
  position: absolute;
  left: 0; right: 0; bottom: 0;
  padding: 12px 16px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  color: var(--warm);
  background: linear-gradient(0deg, rgba(14, 27, 46, 0.88), rgba(14, 27, 46, 0));
}
.media--framed::after {
  content: "";
  position: absolute;
  inset: 8px;
  border: 1px solid rgba(255, 198, 26, 0.35);
  border-radius: calc(var(--r-lg) - 8px);
  pointer-events: none;
}
.media-grid {
  display: grid;
  gap: var(--gap);
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

/* ---------- 17. 显现动效 ---------- */
html.has-reveal [data-reveal] {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.3s ease, transform 0.3s ease;
}
html.has-reveal [data-reveal].is-in { opacity: 1; transform: none; }

/* ---------- 18. 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: clamp(40px, 7vw, 92px);
  padding-bottom: 28px;
  background:
    radial-gradient(120% 90% at 10% -10%, rgba(31, 122, 77, 0.38), transparent 62%),
    var(--night);
  color: var(--warm);
}
.footer-rule {
  height: 16px;
  border-top: 1px solid rgba(31, 122, 77, 0.8);
  background-image: repeating-linear-gradient(90deg, rgba(255, 198, 26, 0.5) 0 1px, transparent 1px 34px);
  background-repeat: repeat-x;
  background-size: auto 8px;
}
.footer-inner {
  display: grid;
  gap: clamp(24px, 4vw, 48px);
  grid-template-columns: minmax(0, 1.2fr) minmax(0, 2fr);
  padding-top: clamp(30px, 5vw, 58px);
}
.footer-brand-name {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(22px, 2.6vw, 30px);
  letter-spacing: -0.01em;
}
.footer-tagline {
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: rgba(255, 198, 26, 0.85);
}
.footer-note {
  margin-top: 14px;
  max-width: 32em;
  font-size: 14px;
  line-height: 1.75;
  color: rgba(246, 243, 236, 0.62);
}
.footer-cols {
  display: grid;
  gap: clamp(20px, 3vw, 32px);
  grid-template-columns: repeat(3, minmax(0, 1fr));
}
.footer-col-title {
  margin-bottom: 12px;
  font-family: var(--font-mono);
  font-weight: 400;
  font-size: 11.5px;
  letter-spacing: 0.18em;
  color: var(--siren);
}
.footer-list { display: grid; gap: 9px; }
.footer-list a {
  display: inline-block;
  padding-bottom: 2px;
  border-bottom: 1px solid transparent;
  font-size: 15px;
  color: rgba(246, 243, 236, 0.82);
  transition: color 0.16s ease, border-color 0.16s ease;
}
.footer-list a:hover { color: #fff; border-bottom-color: var(--siren); }
.footer-contact {
  grid-column: 1 / -1;
  display: grid;
  gap: 8px;
  padding-top: clamp(16px, 2.5vw, 26px);
  border-top: 1px dashed rgba(31, 122, 77, 0.7);
}
.footer-contact__line {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 14px;
  letter-spacing: 0.04em;
  color: rgba(246, 243, 236, 0.78);
  max-width: none;
  word-break: break-word;
}
.footer-contact__label {
  display: inline-block;
  min-width: 5.2em;
  margin-right: 10px;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--siren);
}
.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 24px;
  margin-top: clamp(20px, 3vw, 32px);
  padding-top: 16px;
  border-top: 1px solid rgba(31, 122, 77, 0.5);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: rgba(246, 243, 236, 0.55);
}
.footer-legal, .footer-icp { max-width: none; }

.to-top {
  position: fixed;
  right: clamp(14px, 2.4vw, 26px);
  bottom: clamp(14px, 2.4vw, 26px);
  z-index: 95;
  width: 54px;
  height: 54px;
  display: grid;
  place-content: center;
  gap: 1px;
  border: 1px solid rgba(255, 198, 26, 0.55);
  border-radius: 20px 20px 20px 7px;
  background: var(--night);
  color: var(--siren);
  cursor: pointer;
  box-shadow: 0 16px 32px -20px rgba(16, 20, 24, 0.95);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease, background-color 0.16s ease, color 0.16s ease, visibility 0.2s;
}
.to-top[data-visible] { opacity: 1; visibility: visible; transform: none; }
.to-top:hover { background: var(--night-2); color: #fff; }
.to-top__glyph { font-size: 17px; line-height: 1; }
.to-top__label {
  font-family: var(--font-mono);
  font-size: 9px;
  letter-spacing: 0.16em;
  color: rgba(246, 243, 236, 0.7);
}

/* ---------- 19. 平板与移动 ---------- */
@media (max-width: 1079px) {
  .grid-12 { grid-template-columns: repeat(6, minmax(0, 1fr)); }
  .col-3, .col-4, .col-5, .col-6,
  .col-7, .col-8, .col-9, .col-12 { grid-column: 1 / -1; }
  .footer-inner { grid-template-columns: 1fr; }
  .footer-cols { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}
@media (max-width: 900px) {
  .split { grid-template-columns: 1fr; }
  .toc { position: static; }
}
@media (max-width: 640px) {
  body { font-size: 16.5px; }
  .brand-tagline { display: none; }
  .index-row { grid-template-columns: 62px minmax(0, 1fr); }
  .index-row__meta { grid-column: 2 / -1; }
  .index-row__summary { grid-column: 1 / -1; }
  .footer-cols { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 420px) {
  .footer-cols { grid-template-columns: 1fr; }
  .to-top { width: 48px; height: 48px; }
}

/* ---------- 20. 桌面：左侧框架式导航 ---------- */
@media (min-width: 1080px) {
  html { scroll-padding-top: 24px; }
  body { padding-top: var(--line); padding-left: var(--rail-w); }
  #main-content { scroll-margin-top: 20px; }
  .site-header {
    top: 0; left: 0; bottom: 0; right: auto;
    width: var(--rail-w);
    min-height: 0;
    flex-direction: column;
    align-items: stretch;
    justify-content: flex-start;
    gap: 0;
    padding: calc(var(--line) + 22px) 0 20px;
    border-bottom: 0;
    border-right: 1px solid rgba(31, 122, 77, 0.75);
    overflow: hidden;
  }
  .brand { padding: 0 18px; gap: 12px; }
  .brand-mark { width: 38px; height: 38px; }
  .brand-name { font-size: 18px; }
  .nav-toggle { display: none; }
  .site-nav {
    position: static;
    flex: 1 1 auto;
    max-height: none;
    overflow-y: auto;
    margin-top: 26px;
    opacity: 1;
    visibility: visible;
    background: transparent;
    border-bottom: 0;
  }
  .site-nav[data-open] { max-height: none; padding-bottom: 0; }
  .nav-caption { margin: 0 18px 12px; }
  .nav-link { padding: 12px 18px; }
  .nav-tail { margin-top: 22px; padding: 0 18px; }
  .toc { top: 24px; }
}

/* ---------- 21. 无障碍：减少动效 ---------- */
@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;
  }
  html.has-reveal [data-reveal] { opacity: 1; transform: none; }
}