:root {
  --color-surface: #2d282d;
  --color-surface-alt: #3c363c;
  --color-surface-deep: #4d474d;
  --color-ink: #cfc4cf;
  --color-ink-soft: #a38fa3;
  --color-ink-muted: #8b748b;
  --color-line: #4a444a;
  --color-primary: #d827d7;
  --color-primary-ink: #181118;
  --color-primary-soft: #452845;
  --color-accent: #0ef18d;
  --color-accent-ink: #181118;
  --color-highlight: #274c3e;
  --color-focus: #01fe8f;
  --color-contrast-surface: #efecef;
  --color-contrast-ink: #332e33;
  --color-contrast-line: #c6c2c6;
  --color-contrast-accent: #077946;
  --overlay-scrim: linear-gradient(180deg, rgba(239, 236, 239, 0.35) 0%, rgba(239, 236, 239, 0.72) 55%, rgba(239, 236, 239, 0.92) 100%);
  --font-heading: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-body: "PingFang SC", "HarmonyOS Sans SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 10.1px;
  --text-sm: 14.3px;
  --text-base: 17px;
  --text-lg: 24.0px;
  --text-xl: 34.0px;
  --text-2xl: 48.1px;
  --text-3xl: 68.0px;
  --text-4xl: 96.1px;
  --text-display: clamp(37px, 7.7vw, 98px);
  --text-figure: clamp(31px, 5.5vw, 71px);
  --weight-heading: 660;
  --weight-body: 400;
  --leading-body: 1.83;
  --leading-heading: 1.24;
  --tracking-heading: -0.001em;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 15px;
  --radius-pill: 999px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: 0 0 0 1px rgba(14, 241, 141, 0.35);
  --shadow-2: 0 0 28px rgba(14, 241, 141, 0.35);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1140px;
  --measure: 68ch;
  --gutter: 24px;
  --section-y: 84px;
  --section-y-lg: 118px;
}

/* ---------- reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  background-color: var(--color-surface);
  background-image:
    radial-gradient(1100px 560px at 10% -10%, color-mix(in srgb, var(--color-primary) 13%, transparent), transparent 70%),
    radial-gradient(880px 520px at 92% 4%, color-mix(in srgb, var(--color-accent) 8%, transparent), transparent 72%);
  background-repeat: no-repeat;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
img, svg, video { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
ul, ol { margin: 0; padding: 0; list-style: none; }
h1, h2, h3, h4, p, figure, blockquote { margin: 0; }
strong { font-weight: var(--weight-heading); }
:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ---------- 中文排版与通用文字 ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}
p { overflow-wrap: break-word; }
.display-title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 1.03;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}
.section-title { font-size: var(--text-xl); }
.sub-title { font-size: var(--text-lg); }
.mono-label,
.eyebrow,
.chip,
.footer-title,
.footer-meta,
.breadcrumb,
.toc-title,
.btn,
.contact-link {
  font-family: var(--font-mono);
}
.eyebrow {
  display: inline-block;
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.mono-label {
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.index-num {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-figure);
  line-height: 0.9;
  color: color-mix(in srgb, var(--color-primary) 88%, transparent);
  letter-spacing: -0.02em;
}
.metric-value {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-figure);
  line-height: 1;
  color: var(--color-accent);
}
.lede { color: var(--color-ink-soft); font-size: var(--text-lg); line-height: 1.7; }

/* ---------- 跳至主要内容 ---------- */
.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -120px;
  z-index: 200;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  transition: top 0.2s ease;
}
.skip-link:focus { top: var(--space-2); }

/* ---------- 头部 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  background: transparent;
  border-bottom: var(--border-thin) solid transparent;
  transition: background 0.35s ease, border-color 0.35s ease, box-shadow 0.35s ease;
}
.site-header[data-scrolled="true"],
.site-header[data-open="true"] {
  background: color-mix(in srgb, var(--color-surface) 92%, transparent);
  border-bottom-color: color-mix(in srgb, var(--color-primary) 48%, transparent);
  box-shadow: 0 14px 34px color-mix(in srgb, var(--color-primary) 12%, transparent);
  -webkit-backdrop-filter: blur(14px);
  backdrop-filter: blur(14px);
}
.header-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--gutter);
  min-height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}
.brand { display: inline-flex; align-items: center; gap: 12px; color: var(--color-ink); }
.brand-mark {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: conic-gradient(from 210deg, var(--color-primary), var(--color-accent), var(--color-primary));
  box-shadow: var(--shadow-1), 0 0 20px color-mix(in srgb, var(--color-primary) 45%, transparent);
  flex: none;
}
.brand-text { display: flex; flex-direction: column; line-height: 1.1; }
.brand-name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  letter-spacing: 0.06em;
}
.brand-sub {
  margin-top: 3px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.site-nav { display: flex; align-items: center; }
.nav-list { display: flex; align-items: center; gap: 4px; }
.nav-link {
  display: inline-block;
  padding: 9px 13px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease;
}
.nav-link:hover {
  color: var(--color-ink);
  border-color: color-mix(in srgb, var(--color-primary) 45%, transparent);
  background: color-mix(in srgb, var(--color-primary) 10%, transparent);
}
.nav-link[aria-current="page"] {
  color: var(--color-ink);
  border-color: color-mix(in srgb, var(--color-primary) 75%, transparent);
  background: color-mix(in srgb, var(--color-primary-soft) 55%, transparent);
  box-shadow: var(--shadow-1);
}
.header-actions { display: flex; align-items: center; gap: var(--space-2); }
.header-cta { display: inline-flex; }
.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 9px 13px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 45%, transparent);
  border-radius: var(--radius-pill);
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
}
.nav-toggle-bars {
  display: block;
  width: 16px;
  height: 2px;
  background: currentColor;
  box-shadow: 0 -5px 0 currentColor, 0 5px 0 currentColor;
}
.scroll-progress {
  position: absolute;
  left: 0;
  bottom: -1px;
  height: 2px;
  width: 0;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  box-shadow: var(--shadow-2);
  transition: width 0.12s linear;
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 18px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-primary) 60%, transparent);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--color-primary) 14%, transparent);
  color: var(--color-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
}
.btn:hover {
  border-color: color-mix(in srgb, var(--color-primary) 90%, transparent);
  background: color-mix(in srgb, var(--color-primary) 24%, transparent);
  box-shadow: var(--shadow-1);
}
.btn-primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn-primary:hover {
  background: color-mix(in srgb, var(--color-primary) 84%, var(--color-ink));
  color: var(--color-primary-ink);
  box-shadow: var(--shadow-2);
}
.btn-accent {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}
.btn-accent:hover {
  background: color-mix(in srgb, var(--color-accent) 84%, var(--color-ink));
  color: var(--color-accent-ink);
  box-shadow: var(--shadow-2);
}
.btn-ghost { background: transparent; color: var(--color-ink-soft); }
.btn-ghost:hover { color: var(--color-ink); }

/* ---------- 布局容器 ---------- */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--gutter);
}
.section {
  max-width: var(--container);
  margin: 0 auto;
  padding: var(--section-y) var(--gutter);
}
.section-lg { padding-top: var(--section-y-lg); padding-bottom: var(--section-y-lg); }
.prose { max-width: var(--measure); }
.measure { max-width: var(--measure); }
.prose p + p { margin-top: var(--space-3); }
.prose h2 { margin-top: var(--space-6); font-size: var(--text-xl); }
.prose h3 { margin-top: var(--space-4); font-size: var(--text-lg); }
.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
}
.col-4 { grid-column: span 4; }
.col-6 { grid-column: span 6; }
.col-8 { grid-column: span 8; }

/* ---------- 分隔语言 ---------- */
.rule-dotted {
  border: 0;
  border-top: var(--border-thin) dashed var(--color-line);
  margin: var(--space-6) 0;
}
.rule-sand {
  border: 0;
  height: 1px;
  margin: var(--space-6) 0;
  background-image: repeating-linear-gradient(90deg, var(--color-line) 0 6px, transparent 6px 14px);
}
.sand-trail {
  height: 10px;
  background-image: radial-gradient(circle, color-mix(in srgb, var(--color-primary) 70%, transparent) 1px, transparent 1.6px);
  background-size: 14px 10px;
  opacity: 0.5;
  animation: sand-drift 22s linear infinite;
}
@keyframes sand-drift {
  from { background-position: 0 0; }
  to { background-position: 140px 0; }
}

/* ---------- 标签 ---------- */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 11px;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 45%, transparent);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--color-accent) 8%, transparent);
  color: var(--color-accent);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
}
.chip-warm {
  border-color: color-mix(in srgb, var(--color-primary) 55%, transparent);
  background: color-mix(in srgb, var(--color-primary) 12%, transparent);
  color: color-mix(in srgb, var(--color-primary) 78%, var(--color-ink));
}
.tag-row { display: flex; flex-wrap: wrap; gap: var(--space-2); }

/* ---------- 卡片与面板 ---------- */
.card {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
  transition: border-color 0.25s ease, background-color 0.25s ease, box-shadow 0.25s ease;
}
.card:hover {
  border-color: color-mix(in srgb, var(--color-primary) 55%, transparent);
  background: var(--color-surface-deep);
  box-shadow: var(--shadow-1);
}
.card-link { display: block; }
.panel-contrast {
  padding: var(--space-6);
  border-radius: var(--radius-lg);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.panel-contrast a { border-bottom: 1px dashed var(--color-contrast-line); }
.panel-contrast a:hover { color: var(--color-contrast-accent); border-bottom-color: var(--color-contrast-accent); }
.panel-note {
  padding: var(--space-3) var(--space-4);
  border-left: 3px solid var(--color-accent);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  background: color-mix(in srgb, var(--color-highlight) 60%, var(--color-surface-alt));
  color: var(--color-ink);
}

/* ---------- 折叠块 ---------- */
.fold {
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
  overflow: hidden;
}
.fold + .fold { margin-top: var(--space-2); }
.fold-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-3);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-base);
  cursor: pointer;
  list-style: none;
}
.fold-summary::-webkit-details-marker { display: none; }
.fold-summary::after {
  content: "+";
  font-family: var(--font-mono);
  color: var(--color-accent);
  font-size: var(--text-lg);
  line-height: 1;
}
.fold[open] .fold-summary::after { content: "–"; }
.fold[open] {
  border-color: color-mix(in srgb, var(--color-primary) 55%, transparent);
  box-shadow: var(--shadow-1);
}
.fold-body { padding: 0 var(--space-3) var(--space-3); color: var(--color-ink-soft); }

/* ---------- 图片容器（图录式统一比例） ---------- */
.figure { margin: 0; }
.figure-frame {
  position: relative;
  overflow: hidden;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
  transition: border-color 0.25s ease, box-shadow 0.25s ease;
}
.figure-frame:hover {
  border-color: color-mix(in srgb, var(--color-primary) 55%, transparent);
  box-shadow: var(--shadow-1);
}
.figure-media {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
  aspect-ratio: 16 / 9;
}
.figure-frame[data-ratio="4x3"] .figure-media { aspect-ratio: 4 / 3; }
.figure-frame[data-ratio="1x1"] .figure-media { aspect-ratio: 1 / 1; }
.figure-frame[data-ratio="21x9"] .figure-media { aspect-ratio: 21 / 9; }
.figure-veil {
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
}
.figure-overlay-text {
  position: absolute;
  left: var(--space-3);
  right: var(--space-3);
  bottom: var(--space-3);
  color: var(--color-contrast-ink);
}
.figure-caption {
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

/* ---------- 面包屑 ---------- */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.breadcrumb-item { display: inline-flex; align-items: center; gap: 8px; }
.breadcrumb-item + .breadcrumb-item::before {
  content: "/";
  color: color-mix(in srgb, var(--color-line) 140%, transparent);
}
.breadcrumb-item a:hover { color: var(--color-accent); }

/* ---------- 章节目录 ---------- */
.toc {
  position: sticky;
  top: 96px;
  padding-left: var(--space-3);
  border-left: 2px solid var(--color-line);
}
.toc-title {
  display: block;
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.toc-link {
  display: block;
  padding: 8px 0;
  border-bottom: var(--border-thin) dashed color-mix(in srgb, var(--color-line) 80%, transparent);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  transition: color 0.2s ease, border-color 0.2s ease;
}
.toc-link:hover { color: var(--color-ink); }
.toc-link.is-active {
  color: var(--color-accent);
  border-bottom-color: color-mix(in srgb, var(--color-accent) 60%, transparent);
}

/* ---------- 对照表 ---------- */
.table-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
}
.compare-table {
  width: 100%;
  min-width: 640px;
  border-collapse: collapse;
  font-size: var(--text-sm);
}
.compare-table th,
.compare-table td {
  padding: var(--space-3);
  text-align: left;
  border-bottom: var(--border-thin) dashed color-mix(in srgb, var(--color-line) 80%, transparent);
}
.compare-table th {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.compare-table tr:last-child td { border-bottom: 0; }

/* ---------- 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: var(--section-y-lg);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-top: var(--border-thick) solid color-mix(in srgb, var(--color-primary) 55%, transparent);
}
.footer-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--gutter);
}
.footer-top {
  display: grid;
  grid-template-columns: 1.1fr 0.75fr 1.15fr;
  gap: var(--space-6);
  padding: var(--section-y) 0 var(--space-8);
}
.footer-brand-name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  letter-spacing: 0.05em;
  color: var(--color-contrast-ink);
}
.footer-line {
  margin-top: var(--space-2);
  max-width: 32ch;
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 82%, var(--color-contrast-surface));
}
.footer-meta {
  margin-top: var(--space-3);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-contrast-accent);
}
.footer-title {
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--color-contrast-ink) 62%, var(--color-contrast-surface));
}
.footer-links { margin-top: var(--space-3); display: grid; gap: 10px; }
.footer-links a {
  display: inline-block;
  padding-bottom: 2px;
  border-bottom: 1px solid transparent;
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
  transition: color 0.2s ease, border-color 0.2s ease;
}
.footer-links a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}
.footer-contact {
  padding: var(--space-3) var(--space-3) var(--space-4);
  border-left: 3px solid var(--color-contrast-accent);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  background: color-mix(in srgb, var(--color-contrast-accent) 7%, var(--color-contrast-surface));
}
.footer-contact-list { margin-top: var(--space-3); display: grid; gap: 12px; }
.contact-link {
  display: inline-block;
  padding-bottom: 3px;
  border-bottom: 1px dashed var(--color-contrast-line);
  font-size: var(--text-sm);
  color: var(--color-contrast-ink);
  overflow-wrap: anywhere;
  transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease;
}
.contact-link:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}
.contact-link[data-contact-primary] {
  padding: 10px 15px;
  border: 0;
  border-radius: var(--radius-sm);
  background: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
}
.contact-link[data-contact-primary]:hover {
  background: color-mix(in srgb, var(--color-contrast-accent) 82%, var(--color-contrast-ink));
  color: var(--color-contrast-surface);
}
.footer-address {
  margin-top: var(--space-3);
  font-size: var(--text-sm);
  font-style: normal;
  color: color-mix(in srgb, var(--color-contrast-ink) 78%, var(--color-contrast-surface));
}
.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-3) 0 var(--space-6);
  border-top: 1px dashed var(--color-contrast-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: color-mix(in srgb, var(--color-contrast-ink) 74%, var(--color-contrast-surface));
}
.footer-legal { display: flex; flex-wrap: wrap; gap: var(--space-3); }
.footer-legal a {
  padding-bottom: 2px;
  border-bottom: 1px solid var(--color-contrast-line);
  transition: color 0.2s ease, border-color 0.2s ease;
}
.footer-legal a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

/* ---------- 返回顶部 ---------- */
.to-top {
  position: fixed;
  right: var(--gutter);
  bottom: var(--gutter);
  z-index: 70;
  width: 46px;
  height: 46px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: var(--border-thin) solid color-mix(in srgb, var(--color-accent) 55%, transparent);
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--color-surface-alt) 94%, transparent);
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: var(--text-base);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s ease;
}
.to-top.is-visible { opacity: 1; visibility: visible; transform: none; }
.to-top:hover { box-shadow: var(--shadow-2); }

/* ---------- 平板 ---------- */
@media (max-width: 1023px) {
  .footer-top { grid-template-columns: 1fr 1fr; }
  .footer-contact { grid-column: span 2; }
}
@media (max-width: 880px) {
  .col-4, .col-6, .col-8 { grid-column: span 12; }
}

/* ---------- 移动端导航 ---------- */
@media (max-width: 899px) {
  .header-inner { min-height: 66px; }
  .header-cta { display: none; }
  .nav-toggle { display: inline-flex; }
  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    display: none;
    padding: var(--space-3) var(--gutter) var(--space-4);
    background: color-mix(in srgb, var(--color-surface-alt) 97%, transparent);
    border-bottom: var(--border-thin) solid color-mix(in srgb, var(--color-primary) 50%, transparent);
    -webkit-backdrop-filter: blur(16px);
    backdrop-filter: blur(16px);
  }
  .site-header[data-open="true"] .site-nav { display: block; }
  .nav-list { flex-direction: column; align-items: stretch; gap: 2px; }
  .nav-link {
    display: block;
    padding: 14px var(--space-3);
    border-radius: var(--radius-sm);
    font-size: var(--text-base);
  }
  .toc { position: static; margin-bottom: var(--space-6); }
}

/* ---------- 小屏 ---------- */
@media (max-width: 640px) {
  .brand-sub { display: none; }
  .footer-top { grid-template-columns: 1fr; gap: var(--space-6); padding: var(--section-y) 0 var(--space-6); }
  .footer-contact { grid-column: auto; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
  .section { padding: var(--section-y) var(--gutter); }
}

/* ---------- 焦点与动效偏好 ---------- */
:focus-visible { outline-color: var(--color-focus); }
@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;
  }
  .sand-trail { animation: none; }
  .to-top { transform: none; }
}