/* =====================================================
   IM赛场 · 共享层 /assets/site.css
   深蓝轨道 + 奶油纸页 + 亮橙编号 + 荧光绿数据点
   ===================================================== */

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

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

body, h1, h2, h3, h4, p, ul, ol, figure, blockquote, dl, dd {
  margin: 0;
}
ul, ol { padding: 0; }
img, svg { max-width: 100%; display: block; }
button { font: inherit; }

:root {
  --ink-deep: #0B1F3A;
  --ink-mid: #14345C;
  --orange: #FF6A13;
  --orange-deep: #C2410C;
  --neon: #7CE23C;
  --cream: #F6EFE2;
  --paper-line: #E3D9C6;
  --ink: #1C1712;
  --ink-soft: #D8E3F4;
  --white: #FFFFFF;

  --rail-w: 104px;
  --container: 1240px;
  --header-h: 86px;

  --radius-s: 8px;
  --radius-m: 16px;
  --radius-l: 28px;
  --shadow-card: 0 18px 40px -26px rgba(11, 31, 58, .55);
  --shadow-float: 0 30px 56px -30px rgba(11, 31, 58, .8);

  --font-display: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-editorial: "Source Han Serif SC", "Noto Serif SC", "Songti SC", "SimSun", Georgia, serif;
  --font-body: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", "Roboto Mono", "SFMono-Regular", Consolas, "Courier New", monospace;
}

body {
  padding-left: var(--rail-w);
  font-family: var(--font-body);
  font-size: 17px;
  font-weight: 400;
  line-height: 1.75;
  letter-spacing: .01em;
  color: var(--ink);
  background: var(--cream);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 900;
  line-height: 1.2;
  letter-spacing: .01em;
}
h1, h2 { text-wrap: balance; }
p { text-wrap: pretty; }
a { color: var(--orange-deep); text-decoration-thickness: 1px; text-underline-offset: 3px; }

::selection { background: var(--orange); color: var(--ink-deep); }

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

#main-content { scroll-margin-top: calc(var(--header-h) + 16px); }

/* ---------- 工具类 ---------- */
.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;
}
.skip-link {
  position: fixed; top: -80px; left: calc(var(--rail-w) + 16px);
  z-index: 300;
  padding: 12px 20px;
  border-radius: 0 0 14px 14px;
  background: var(--orange); color: var(--ink-deep);
  font-family: var(--font-display); font-weight: 800; font-size: 15px;
  text-decoration: none;
  transition: top .2s ease;
}
.skip-link:focus { top: 0; }

.mono, .num { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

/* ---------- 左侧品牌轨道 ---------- */
.site-rail {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  width: var(--rail-w);
  z-index: 90;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  padding: 22px 0 26px;
  color: var(--ink-soft);
  background: linear-gradient(180deg, #0B1F3A 0%, #0B1F3A 58%, #14345C 100%);
  border-right: 1px solid rgba(216, 227, 244, .12);
}
.site-rail__mark {
  display: grid; place-items: center;
  width: 44px; height: 44px;
  border-radius: 14px 14px 14px 4px;
  background: var(--orange);
  color: var(--ink-deep);
  font-family: var(--font-display); font-weight: 900; font-size: 16px;
  transform: skewX(-6deg);
}
.site-rail__label {
  writing-mode: vertical-rl;
  font-size: 11px;
  letter-spacing: .32em;
  color: rgba(216, 227, 244, .55);
}
.site-rail__line {
  flex: 1;
  width: 1px;
  margin: 18px 0;
  background: linear-gradient(180deg, rgba(216,227,244,.35), rgba(124,226,60,.6), rgba(216,227,244,.08));
}
.site-rail__num {
  font-family: var(--font-mono);
  font-size: 20px; font-weight: 700;
  letter-spacing: .04em;
  color: var(--orange);
  font-variant-numeric: tabular-nums;
}

/* ---------- 头部 ---------- */
.site-header {
  position: fixed;
  top: 0; left: var(--rail-w); right: 0;
  z-index: 80;
  color: var(--ink-soft);
  background: transparent;
  border-bottom: 1px solid rgba(216, 227, 244, .16);
  transition: background-color .25s ease, border-color .25s ease, color .25s ease, box-shadow .25s ease;
}
.site-header[data-state="solid"] {
  background: var(--cream);
  color: var(--ink);
  border-bottom-color: var(--paper-line);
  box-shadow: 0 14px 32px -26px rgba(11, 31, 58, .7);
}
.site-header__inner {
  width: min(100%, var(--container));
  margin: 0 auto;
  padding: 20px 32px;
  display: flex;
  align-items: center;
  gap: 28px;
  transition: padding .25s ease;
}
.site-header[data-state="solid"] .site-header__inner { padding: 8px 32px; }

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
  flex: 0 0 auto;
}
.brand__mark {
  display: grid; place-items: center;
  width: 42px; height: 42px;
  border-radius: 13px 13px 13px 4px;
  background: var(--orange);
  color: var(--ink-deep);
  font-family: var(--font-display); font-weight: 900; font-size: 17px;
  transform: skewX(-6deg);
}
.brand__text { display: block; }
.brand__name {
  display: block;
  font-family: var(--font-display);
  font-weight: 900; font-size: 20px; line-height: 1.1;
  letter-spacing: .02em;
}
.brand__tagline {
  display: block;
  font-size: 12px;
  letter-spacing: .12em;
  opacity: .68;
}

/* 导航 */
.primary-nav {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-left: auto;
}
.primary-nav__list {
  display: flex;
  align-items: center;
  gap: 4px;
  list-style: none;
}
.primary-nav__list a {
  display: inline-block;
  padding: 8px 12px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 500;
  color: inherit;
  text-decoration: none;
  transition: color .2s ease, background-color .2s ease;
}
.primary-nav__list a:hover {
  color: var(--white);
  background: rgba(255, 106, 19, .2);
}
.primary-nav__list a[aria-current="page"] { color: var(--orange); font-weight: 700; }
.primary-nav__list a[aria-current="page"]::after {
  content: "";
  display: block;
  height: 2px;
  margin-top: 3px;
  border-radius: 2px;
  background: var(--orange);
}
.site-header[data-state="solid"] .primary-nav__list a { color: var(--ink-mid); }
.site-header[data-state="solid"] .primary-nav__list a:hover { color: var(--ink); background: rgba(255, 106, 19, .14); }
.site-header[data-state="solid"] .primary-nav__list a[aria-current="page"] { color: var(--orange-deep); }
.primary-nav__actions { display: flex; gap: 10px; }

/* 移动菜单按钮 */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 9px;
  margin-left: auto;
  padding: 9px 15px;
  border-radius: 999px;
  border: 1.5px solid rgba(216, 227, 244, .45);
  background: transparent;
  color: inherit;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: border-color .2s ease, background-color .2s ease;
}
.nav-toggle:hover { border-color: var(--orange); }
.site-header[data-state="solid"] .nav-toggle { border-color: rgba(28, 23, 18, .28); }
.nav-toggle__bars { display: grid; gap: 4px; }
.nav-toggle__bars span {
  display: block; width: 16px; height: 2px;
  border-radius: 2px; background: currentColor;
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* 滚动进度 */
.scroll-progress {
  position: absolute;
  left: 0; right: 0; bottom: -2px;
  height: 3px;
  overflow: hidden;
}
.scroll-progress__bar {
  display: block;
  width: 100%; height: 100%;
  background: linear-gradient(90deg, var(--orange), var(--neon));
  transform: scaleX(0);
  transform-origin: left center;
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 13px 22px;
  border: 1.5px solid transparent;
  border-radius: 999px;
  background: var(--orange);
  color: var(--ink-deep);
  font-family: var(--font-display);
  font-weight: 800; font-size: 15px;
  letter-spacing: .02em;
  text-decoration: none;
  cursor: pointer;
  transition: transform .2s ease, background-color .2s ease, color .2s ease, border-color .2s ease;
}
.btn:hover { background: var(--orange-deep); color: var(--white); transform: translateY(-2px); }
.btn--primary { background: var(--orange); color: var(--ink-deep); }
.btn--ghost {
  background: transparent;
  border-color: rgba(216, 227, 244, .42);
  color: var(--ink-soft);
}
.btn--ghost:hover {
  background: rgba(216, 227, 244, .12);
  border-color: var(--orange);
  color: var(--white);
}
.site-header[data-state="solid"] .btn--ghost {
  border-color: rgba(28, 23, 18, .26);
  color: var(--ink);
}
.site-header[data-state="solid"] .btn--ghost:hover { background: rgba(255, 106, 19, .14); color: var(--ink-deep); }
.btn--outline {
  background: transparent;
  border-color: var(--orange);
  color: var(--orange);
}
.btn--outline:hover { background: var(--orange); color: var(--ink-deep); }
.btn--sm { padding: 9px 15px; font-size: 13px; }

/* ---------- 容器与分区 ---------- */
.container {
  width: min(100%, var(--container));
  margin-inline: auto;
  padding-inline: 32px;
}
.section { padding: 96px 0; position: relative; }
.section--tight { padding: 58px 0; }
.section--dark { background: var(--ink-deep); color: var(--ink-soft); }
.section--mid { background: var(--ink-mid); color: var(--ink-soft); }
.section--cream {
  background:
    linear-gradient(180deg, rgba(227, 217, 198, .35) 0%, rgba(227, 217, 198, 0) 120px),
    var(--cream);
  color: var(--ink);
}
.section--dark h1, .section--dark h2, .section--dark h3,
.section--mid h1, .section--mid h2, .section--mid h3 { color: var(--white); }

.edge-slant {
  display: block;
  height: 64px;
  background: var(--ink-deep);
  clip-path: polygon(0 0, 100% 0, 100% 34%, 0 100%);
}
.divider { height: 1px; background: var(--paper-line); border: 0; }

/* ---------- 章节体系 ---------- */
.chapter-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 26px;
  align-items: start;
  margin-bottom: 32px;
}
.chapter-num {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(46px, 6.4vw, 84px);
  line-height: .84;
  letter-spacing: -.02em;
  color: var(--orange);
  transform: skewX(-4deg);
  font-variant-numeric: tabular-nums;
}
.chapter-title { font-size: clamp(22px, 3vw, 30px); }
.chapter-claim {
  margin-top: 8px;
  max-width: 60ch;
  font-size: 16px;
  opacity: .82;
}

/* ---------- 栅格 ---------- */
.grid { display: grid; gap: 26px; }
.grid--7-5 { grid-template-columns: 7fr 5fr; }
.grid--8-4 { grid-template-columns: 8fr 4fr; }
.grid--auto { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }

/* ---------- 卡片 ---------- */
.card {
  position: relative;
  padding: 26px;
  border-radius: var(--radius-m);
  background: var(--white);
  color: var(--ink);
  border: 1px solid rgba(28, 23, 18, .07);
  box-shadow: var(--shadow-card);
  transition: transform .2s ease, box-shadow .2s ease;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow-float); }
.card--dark {
  background: var(--ink-mid);
  color: var(--ink-soft);
  border-color: rgba(216, 227, 244, .16);
}
.card--dark h3 { color: var(--white); }
.card--float { box-shadow: var(--shadow-float); }
.card__kicker {
  display: block;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--orange);
}
.card--dark .card__kicker { color: var(--neon); }
.card__title { margin: 10px 0 8px; font-size: 22px; }
.card__text { font-size: 16px; line-height: 1.7; }
.card__meta {
  margin-top: 14px;
  font-size: 13px;
  letter-spacing: .06em;
  opacity: .72;
}
.card__list {
  list-style: none;
  margin-top: 12px;
  display: grid;
  gap: 8px;
  font-size: 15px;
}
.card__list li { padding-left: 16px; position: relative; }
.card__list li::before {
  content: "";
  position: absolute; left: 0; top: .68em;
  width: 7px; height: 7px;
  border-radius: 2px;
  background: var(--orange);
  transform: skewX(-8deg);
}

/* ---------- 数据点 ---------- */
.stat { display: grid; gap: 4px; }
.stat__value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(30px, 4vw, 46px);
  font-weight: 700;
  line-height: 1.05;
  color: var(--ink);
}
.section--dark .stat__value, .section--mid .stat__value, .card--dark .stat__value { color: var(--neon); }
.stat__label {
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  opacity: .75;
}

/* ---------- 标签 ---------- */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border-radius: 999px;
  border: 1px solid var(--ink-deep);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: .12em;
  color: var(--ink-deep);
  background: transparent;
}
.tag--orange { background: var(--orange); border-color: var(--orange); color: var(--ink-deep); }
.tag--neon { background: rgba(124, 226, 60, .16); border-color: var(--neon); color: var(--neon); }
.tag--quiet { border-color: var(--paper-line); color: rgba(28, 23, 18, .62); }

/* ---------- 面包屑 ---------- */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  letter-spacing: .06em;
  opacity: .82;
}
.crumbs a { color: inherit; text-decoration: none; border-bottom: 1px solid currentColor; }
.crumbs a:hover { color: var(--orange); border-color: var(--orange); }
.crumbs span[aria-hidden="true"] { opacity: .5; }

/* ---------- 正文排版 ---------- */
.prose { max-width: 68ch; font-size: 17px; line-height: 1.75; }
.prose > * + * { margin-top: 18px; }
.prose h2 { margin-top: 40px; font-size: 28px; }
.prose h3 { margin-top: 30px; font-size: 22px; }
.prose h2, .prose h3, .prose blockquote { font-family: var(--font-editorial); }
.prose blockquote {
  margin: 28px 0;
  padding: 18px 24px;
  border-left: 4px solid var(--orange);
  background: rgba(227, 217, 198, .4);
  font-size: 20px;
  border-radius: 0 var(--radius-m) var(--radius-m) 0;
}
.prose ul, .prose ol { padding-left: 22px; display: grid; gap: 8px; }
.prose code {
  font-family: var(--font-mono);
  font-size: .92em;
  padding: 2px 6px;
  border-radius: 5px;
  background: rgba(11, 31, 58, .08);
}

/* ---------- 表格 ---------- */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 15px;
}
.data-table caption {
  text-align: left;
  padding-bottom: 10px;
  font-size: 12px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--orange-deep);
}
.data-table th, .data-table td {
  padding: 12px 14px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--paper-line);
}
.data-table thead th {
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--ink-mid);
  border-bottom: 2px solid var(--ink-deep);
}
.data-table tbody tr:nth-child(even) { background: rgba(227, 217, 198, .42); }
.data-table td.num { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.data-table--dark { color: var(--ink-soft); }
.data-table--dark thead th { color: var(--white); border-bottom-color: var(--orange); }
.data-table--dark th, .data-table--dark td { border-bottom-color: rgba(216, 227, 244, .16); }
.data-table--dark tbody tr:nth-child(even) { background: rgba(216, 227, 244, .07); }

/* ---------- 折叠问答 ---------- */
.accordion { display: grid; gap: 0; border-top: 1px solid var(--paper-line); }
.accordion__item { border-bottom: 1px solid var(--paper-line); }
.accordion__trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  width: 100%;
  padding: 20px 4px;
  border: 0;
  background: transparent;
  color: inherit;
  text-align: left;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 18px;
  cursor: pointer;
  transition: color .2s ease;
}
.accordion__trigger::after {
  content: "+";
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 20px;
  color: var(--orange);
  transition: transform .2s ease;
}
.accordion__trigger:hover { color: var(--orange-deep); }
.accordion__trigger[aria-expanded="true"]::after { content: "–"; }
.accordion__panel {
  padding: 0 4px 22px;
  font-size: 16px;
  line-height: 1.75;
  opacity: .9;
}
.accordion__panel[hidden] { display: none; }

/* ---------- 分段切换 ---------- */
.segmented {
  display: inline-flex;
  gap: 4px;
  padding: 4px;
  border-radius: 999px;
  background: rgba(11, 31, 58, .1);
}
.segmented__btn {
  padding: 8px 18px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: inherit;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: .04em;
  cursor: pointer;
  transition: background-color .2s ease, color .2s ease;
}
.segmented__btn:hover { color: var(--orange-deep); }
.segmented__btn[aria-pressed="true"] { background: var(--orange); color: var(--ink-deep); }

/* ---------- 图片容器基础规则 ---------- */
.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-m);
  background: linear-gradient(135deg, var(--ink-mid), var(--ink-deep));
  border: 1px solid rgba(216, 227, 244, .14);
}
.media > img { width: 100%; height: 100%; object-fit: cover; }
.media__ph {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  text-align: center;
  padding: 16px;
  font-size: 12px;
  letter-spacing: .16em;
  color: rgba(216, 227, 244, .55);
}
.media--16x9 { aspect-ratio: 16 / 9; }
.media--4x3 { aspect-ratio: 4 / 3; }
.media--1x1 { aspect-ratio: 1 / 1; }
.media--3x4 { aspect-ratio: 3 / 4; }
.media--clip { clip-path: polygon(0 0, 100% 7%, 100% 100%, 0 93%); }
.media__caption {
  margin-top: 10px;
  font-size: 13px;
  letter-spacing: .04em;
  opacity: .75;
}

/* ---------- 滚动显现 ---------- */
html.has-js [data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity .5s ease, transform .5s ease;
}
html.has-js [data-reveal].is-visible { opacity: 1; transform: none; }

/* ---------- 页脚 ---------- */
.site-footer {
  position: relative;
  padding: 74px 0 30px;
  color: var(--ink-soft);
  background:
    radial-gradient(120% 90% at 10% -12%, rgba(255, 106, 19, .3), transparent 58%),
    radial-gradient(90% 80% at 96% 6%, rgba(124, 226, 60, .16), transparent 60%),
    var(--ink-deep);
}
.site-footer::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 6px;
  background: linear-gradient(90deg, var(--orange), var(--neon));
}
.site-footer__inner {
  width: min(100%, var(--container));
  margin-inline: auto;
  padding-inline: 32px;
  display: grid;
  grid-template-columns: minmax(220px, 1.2fr) minmax(0, 2.3fr) minmax(250px, 1.4fr);
  gap: 48px;
}
.site-footer__mark {
  display: grid; place-items: center;
  width: 52px; height: 52px;
  border-radius: 16px 16px 16px 5px;
  background: var(--orange);
  color: var(--ink-deep);
  font-family: var(--font-display); font-weight: 900; font-size: 19px;
  transform: skewX(-6deg);
}
.site-footer__name {
  margin-top: 16px;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: 24px;
  color: var(--white);
}
.site-footer__tagline {
  font-size: 13px;
  letter-spacing: .14em;
  color: var(--neon);
}
.site-footer__meta {
  margin-top: 12px;
  font-size: 13px;
  line-height: 1.7;
  color: rgba(216, 227, 244, .72);
}
.site-footer__nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 28px;
}
.footer-col__title {
  margin-bottom: 14px;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--orange);
}
.footer-col__list { list-style: none; display: grid; gap: 10px; }
.footer-col__list a {
  font-size: 15px;
  color: var(--ink-soft);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color .2s ease, border-color .2s ease;
}
.footer-col__list a:hover { color: var(--white); border-bottom-color: var(--orange); }

.contact-list { list-style: none; display: grid; gap: 12px; }
.contact-list__row {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 10px;
}
.contact-list__key {
  min-width: 44px;
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--neon);
}
.contact-list__value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 14px;
  color: var(--white);
}
.copy-btn {
  padding: 3px 11px;
  border: 1px solid rgba(216, 227, 244, .35);
  border-radius: 999px;
  background: transparent;
  color: var(--ink-soft);
  font-size: 12px;
  cursor: pointer;
  transition: color .2s ease, border-color .2s ease;
}
.copy-btn:hover, .copy-btn[data-copied] { color: var(--neon); border-color: var(--neon); }

.site-footer__bottom {
  width: min(100%, var(--container));
  margin: 54px auto 0;
  padding: 20px 32px 0;
  border-top: 1px solid rgba(216, 227, 244, .14);
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px 24px;
  font-size: 13px;
  color: rgba(216, 227, 244, .72);
}
.site-footer__legal {
  font-family: var(--font-mono);
  letter-spacing: .04em;
}

/* ---------- 平板 ---------- */
@media (max-width: 1180px) {
  .brand__tagline { display: none; }
  .site-footer__inner { grid-template-columns: minmax(200px, 1fr) minmax(0, 2fr); }
  .site-footer__contact { grid-column: 1 / -1; }
}

@media (max-width: 1024px) {
  :root { --rail-w: 0px; --header-h: 70px; }
  .site-rail { display: none; }
  .site-header { left: 0; }
  .site-header__inner { padding: 14px 20px; gap: 16px; }
  .site-header[data-state="solid"] .site-header__inner { padding: 6px 20px; }
  .skip-link { left: 16px; }

  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: fixed;
    top: var(--header-h);
    left: 0; right: 0; bottom: 0;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 22px;
    margin: 0;
    padding: 26px 22px 48px;
    background: var(--ink-deep);
    overflow-y: auto;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity .2s ease, transform .2s ease, visibility .2s ease;
  }
  .primary-nav[data-open] {
    opacity: 1;
    visibility: visible;
    transform: none;
  }
  .primary-nav__list { flex-direction: column; align-items: stretch; gap: 2px; }
  .primary-nav__list a {
    padding: 14px 14px;
    border-radius: 12px;
    font-size: 18px;
    color: var(--ink-soft);
  }
  .primary-nav__list a[aria-current="page"] {
    color: var(--orange);
    background: rgba(255, 106, 19, .16);
  }
  .primary-nav__list a[aria-current="page"]::after { display: none; }
  .site-header[data-state="solid"] .primary-nav__list a { color: var(--ink-soft); }
  .site-header[data-state="solid"] .primary-nav__list a[aria-current="page"] { color: var(--orange); }
  .primary-nav__actions { flex-direction: column; gap: 12px; }
  .primary-nav__actions .btn { width: 100%; padding: 13px 18px; font-size: 15px; }
  .primary-nav__actions .btn--ghost {
    border-color: rgba(216, 227, 244, .42);
    color: var(--ink-soft);
  }
  body[data-nav-open] { overflow: hidden; }

  .section { padding: 72px 0; }
  .container, .site-footer__inner, .site-footer__bottom { padding-inline: 22px; }
  .grid--7-5, .grid--8-4 { grid-template-columns: 1fr; }
  .chapter-head { gap: 18px; }
}

/* ---------- 手机 ---------- */
@media (max-width: 720px) {
  body { font-size: 16px; }
  .section { padding: 58px 0; }
  .chapter-num { font-size: clamp(40px, 14vw, 60px); }
  .site-footer { padding-top: 56px; }
  .site-footer__inner { grid-template-columns: 1fr; gap: 34px; }
  .site-footer__nav { grid-template-columns: 1fr 1fr; gap: 22px; }
  .site-footer__bottom { margin-top: 38px; }
  .card { padding: 20px; }
}

/* ---------- 动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
  }
  html.has-js [data-reveal] { opacity: 1; transform: none; }
  .card:hover, .btn:hover { transform: none; }
}