:root {
  --color-surface: #f7f6f6;
  --color-surface-alt: #eeeded;
  --color-surface-deep: #e3e1e0;
  --color-ink: #4d4441;
  --color-ink-soft: #766966;
  --color-ink-muted: #887a77;
  --color-line: #d8d6d5;
  --color-primary: #cc4c2e;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #f1deda;
  --color-accent: #cd4727;
  --color-accent-ink: #ffffff;
  --color-highlight: #efd6d1;
  --color-focus: #cc3b19;
  --color-contrast-surface: #1a110f;
  --color-contrast-ink: #e7e5e4;
  --color-contrast-line: #47403e;
  --color-contrast-accent: #d85132;
  --overlay-scrim: linear-gradient(180deg, rgba(26, 17, 15, 0.35) 0%, rgba(26, 17, 15, 0.72) 55%, rgba(26, 17, 15, 0.92) 100%);
  --font-heading: "Kaiti SC", STKaiti, KaiTi, "Songti SC", serif;
  --font-body: "Songti SC", "PingFang SC", "Microsoft YaHei", serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 12.9px;
  --text-sm: 16.1px;
  --text-base: 18px;
  --text-lg: 22.5px;
  --text-xl: 28.1px;
  --text-2xl: 35.2px;
  --text-3xl: 43.9px;
  --text-4xl: 54.9px;
  --text-display: clamp(41px, 8.4vw, 107px);
  --text-figure: clamp(34px, 6.0vw, 77px);
  --weight-heading: 421;
  --weight-body: 400;
  --leading-body: 1.97;
  --leading-heading: 1.26;
  --tracking-heading: 0.014em;
  --radius-sm: 1px;
  --radius-md: 2px;
  --radius-lg: 2px;
  --radius-pill: 2px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: none;
  --shadow-2: none;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1020px;
  --measure: 59ch;
  --gutter: 16px;
  --section-y: 110px;
  --section-y-lg: 154px;
}

/* ---- 版面派生常量（仅布局，不涉及色与字号） ---- */
:root {
  --rail-w: 216px;
  --topbar-h: 68px;
  --ease: cubic-bezier(.22, .61, .36, 1);
}

/* ============ reset & base ============ */
*, *::before, *::after { box-sizing: border-box; }

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

body {
  margin: 0;
  min-height: 100vh;
  background-color: var(--color-surface);
  background-image:
    radial-gradient(140% 70% at 6% -14%, color-mix(in srgb, var(--color-ink) 7%, transparent), transparent 60%),
    radial-gradient(80% 50% at 104% -8%, color-mix(in srgb, var(--color-primary) 5%, transparent), transparent 58%);
  background-repeat: no-repeat;
  background-attachment: fixed;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
}

img, svg, video { display: block; max-width: 100%; height: auto; }
button, input, select, textarea { font: inherit; color: inherit; }
a { color: inherit; text-decoration: none; }
ul, ol { margin: 0; padding: 0; list-style: none; }
main { display: block; }

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}
h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4, h5, h6 { font-size: var(--text-lg); }

p { margin: 0 0 var(--space-3); max-width: var(--measure); }
hr { border: 0; border-top: var(--border-thin) solid var(--color-line); margin: var(--space-6) 0; }
blockquote {
  margin: var(--space-4) 0;
  padding-left: var(--space-4);
  border-left: var(--border-thin) solid var(--color-line);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink-soft);
}
code, kbd, samp { font-family: var(--font-mono); font-size: var(--text-sm); }
::selection { background: var(--color-primary-soft); color: var(--color-ink); }
:focus-visible { outline: 2px solid var(--color-focus); outline-offset: 2px; }

.prose ul { list-style: disc; padding-left: 1.4em; margin-bottom: var(--space-3); }
.prose ol { list-style: decimal; padding-left: 1.4em; margin-bottom: var(--space-3); }
.prose li { list-style: inherit; margin-bottom: var(--space-1); }

/* ============ 文字工具 ============ */
.mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.text-xs { font-size: var(--text-xs); }
.text-sm { font-size: var(--text-sm); }
.muted { color: var(--color-ink-muted); }
.soft { color: var(--color-ink-soft); }
.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .24em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.lede { font-size: var(--text-lg); line-height: 1.72; color: var(--color-ink-soft); max-width: var(--measure); }
.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0);
  white-space: nowrap; border: 0;
}
.link {
  color: var(--color-ink);
  background-image: linear-gradient(currentColor, currentColor);
  background-size: 0 var(--border-thin);
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: background-size 200ms var(--ease), color 200ms var(--ease);
}
main a:not([class]) {
  color: var(--color-ink);
  background-image: linear-gradient(currentColor, currentColor);
  background-size: 0 var(--border-thin);
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: background-size 200ms var(--ease), color 200ms var(--ease);
}
.link:hover, main a:not([class]):hover { background-size: 100% var(--border-thin); color: var(--color-accent); }
.link-more {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--font-heading); font-size: var(--text-sm); letter-spacing: .06em;
  color: var(--color-ink);
  transition: color 200ms var(--ease);
}
.link-more::after { content: "→"; font-family: var(--font-mono); transition: transform 200ms var(--ease); }
.link-more:hover { color: var(--color-accent); }
.link-more:hover::after { transform: translateX(4px); }

/* ============ 布局 ============ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.stack { display: flex; flex-direction: column; gap: var(--space-3); }
.cluster { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-2); }
.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-4) var(--gutter);
}
.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-12 { grid-column: span 12; }
.split {
  display: grid;
  grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
  gap: var(--space-6);
}
.rule { height: 0; border: 0; border-top: var(--border-thin) solid var(--color-line); margin: 0; }

/* ============ 章节 ============ */
.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--tight { padding-block: var(--space-8); }
.section--wash { background: var(--color-surface-alt); }
.section-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: var(--space-4);
  align-items: end;
  padding-top: var(--space-3);
  margin-bottom: var(--space-6);
  border-top: var(--border-thin) solid var(--color-line);
}
.section-num {
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  line-height: 1;
  letter-spacing: .02em;
  color: var(--color-ink-muted);
}
.section-title { margin: 0; font-size: var(--text-2xl); }
.section-kicker {
  display: block;
  margin-bottom: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .24em;
  color: var(--color-ink-muted);
}
.section-lede { margin: var(--space-2) 0 0; color: var(--color-ink-soft); max-width: var(--measure); }
.page-head { padding-top: var(--space-8); padding-bottom: var(--space-6); }

/* ============ 面包屑 ============ */
.breadcrumb { margin-bottom: var(--space-4); }
.breadcrumb ol {
  display: flex; flex-wrap: wrap; gap: var(--space-2);
  font-family: var(--font-mono); font-size: var(--text-xs);
  letter-spacing: .08em; color: var(--color-ink-muted);
}
.breadcrumb li { display: inline-flex; align-items: center; }
.breadcrumb li::after { content: "/"; margin-left: var(--space-2); color: var(--color-line); }
.breadcrumb li:last-child::after { content: ""; }
.breadcrumb a { color: var(--color-ink-soft); transition: color 200ms var(--ease); }
.breadcrumb a:hover { color: var(--color-accent); }
.breadcrumb [aria-current="page"] { color: var(--color-ink); }

/* ============ 按钮 ============ */
.btn {
  --btn-bg: transparent;
  --btn-fg: var(--color-ink);
  --btn-line: var(--color-line);
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 18px;
  border: var(--border-thin) solid var(--btn-line);
  border-radius: var(--radius-sm);
  background: var(--btn-bg);
  color: var(--btn-fg);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .06em;
  cursor: pointer;
  transition: background-color 200ms var(--ease), color 200ms var(--ease), border-color 200ms var(--ease);
}
.btn:hover {
  background: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.btn--primary { --btn-bg: var(--color-primary); --btn-fg: var(--color-primary-ink); --btn-line: var(--color-primary); }
.btn--primary:hover { background: var(--color-contrast-surface); border-color: var(--color-contrast-surface); color: var(--color-contrast-ink); }
.btn--ghost { --btn-bg: transparent; --btn-fg: var(--color-ink-soft); }
.btn--contrast { --btn-bg: var(--color-contrast-surface); --btn-fg: var(--color-contrast-ink); --btn-line: var(--color-contrast-surface); }
.btn--contrast:hover { background: var(--color-primary); border-color: var(--color-primary); color: var(--color-primary-ink); }
.btn--sm { padding: 7px 13px; font-size: var(--text-xs); letter-spacing: .1em; }
.btn--block { width: 100%; }
.btn-row { display: flex; flex-wrap: wrap; gap: var(--space-2); margin-top: var(--space-3); }

/* ============ 标签 / 状态 ============ */
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 3px 9px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .08em;
  line-height: 1.7;
}
.chip--contrast { background: var(--color-contrast-surface); color: var(--color-contrast-ink); border-color: var(--color-contrast-surface); }
.chip--primary { background: var(--color-primary); color: var(--color-primary-ink); border-color: var(--color-primary); }
.chip--soft { background: var(--color-primary-soft); color: var(--color-accent); border-color: transparent; }
.status-dot { display: inline-block; width: 6px; height: 6px; border-radius: 50%; background: var(--color-primary); }
.tag-list { display: flex; flex-wrap: wrap; gap: var(--space-1); }
.tag {
  padding-bottom: 2px;
  border-bottom: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .08em;
  color: var(--color-ink-soft);
  transition: color 200ms var(--ease), border-color 200ms var(--ease);
}
.tag:hover { color: var(--color-accent); border-color: var(--color-accent); }

/* ============ 卡片 ============ */
.card {
  display: flex; flex-direction: column; gap: var(--space-2);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
}
.card--paper {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-surface);
}
.card--contrast {
  padding: var(--space-4);
  border: var(--border-thin) solid var(--color-contrast-surface);
  border-radius: var(--radius-md);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.card--contrast .card-title { color: var(--color-contrast-ink); }
.card--contrast .card-meta,
.card--contrast .card-text { color: color-mix(in srgb, var(--color-contrast-ink) 72%, transparent); }
.card--contrast .link-more { color: var(--color-contrast-ink); }
.card-title { margin: 0; font-family: var(--font-heading); font-size: var(--text-lg); line-height: 1.32; }
.card-title a { color: inherit; }
.card-title a:hover { color: var(--color-accent); }
.card-meta {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .1em;
  color: var(--color-ink-muted);
}
.card-text { margin: 0; font-size: var(--text-sm); color: var(--color-ink-soft); max-width: var(--measure); }

/* ============ 图片容器 ============ */
.media-frame {
  position: relative;
  display: block;
  overflow: hidden;
  border-radius: var(--radius-md);
  background: var(--color-surface-deep);
}
.media-frame img { width: 100%; height: 100%; object-fit: cover; }
.media-frame--16x9 { aspect-ratio: 16 / 9; }
.media-frame--4x3 { aspect-ratio: 4 / 3; }
.media-frame--3x4 { aspect-ratio: 3 / 4; }
.media-frame--1x1 { aspect-ratio: 1 / 1; }
.media-frame--21x9 { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 2 / 3; }
.media-overlay { position: absolute; inset: 0; background: var(--overlay-scrim); }
.media-frame--scrim::after {
  content: "";
  position: absolute; inset: 0;
  background: var(--overlay-scrim);
  pointer-events: none;
}
.media-text {
  position: absolute;
  left: var(--space-3); right: var(--space-3); bottom: var(--space-3);
  z-index: 2;
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: var(--leading-heading);
}
.media-caption {
  margin-top: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  max-width: var(--measure);
}

/* ============ 数据 ============ */
.figure { margin: 0; }
.figure-value {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  letter-spacing: -.02em;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}
.figure-unit { margin-left: 4px; font-family: var(--font-mono); font-size: var(--text-sm); color: var(--color-ink-muted); }
.figure-label { margin-top: var(--space-2); font-size: var(--text-sm); color: var(--color-ink-soft); max-width: var(--measure); }
.figure--primary .figure-value { color: var(--color-primary); }
.card--contrast .figure-value { color: var(--color-contrast-ink); }
.card--contrast .figure-unit { color: var(--color-contrast-accent); }
.stat-value {
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  line-height: 1;
  font-variant-numeric: tabular-nums;
}
.stat-label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .14em;
  color: var(--color-ink-muted);
}
[data-hint] { position: relative; }
[data-hint]::after {
  content: attr(data-hint);
  position: absolute;
  left: 50%; bottom: calc(100% + 8px);
  transform: translate(-50%, 4px);
  width: max-content;
  min-width: 14ch; max-width: 34ch;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  background: var(--color-highlight);
  color: var(--color-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  line-height: 1.6;
  letter-spacing: 0;
  text-align: left;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  z-index: 20;
  transition: opacity 180ms var(--ease), transform 180ms var(--ease);
}
[data-hint]:hover::after,
[data-hint]:focus-visible::after { opacity: 1; visibility: visible; transform: translate(-50%, 0); }

/* ============ 表格 ============ */
.table-wrap { overflow-x: auto; border-top: var(--border-thin) solid var(--color-line); }
.data-table { width: 100%; border-collapse: collapse; font-size: var(--text-sm); }
.data-table caption {
  padding: var(--space-2) 0;
  text-align: left;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .1em;
  color: var(--color-ink-muted);
}
.data-table th,
.data-table td {
  padding: 12px var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
  text-align: left;
  vertical-align: baseline;
}
.data-table thead th {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: .08em;
  color: var(--color-ink-soft);
}
.data-table tbody tr:nth-child(even) { background: var(--color-surface-deep); }
.data-table tbody tr:hover { background: var(--color-primary-soft); }
.data-table td.num { font-family: var(--font-mono); font-variant-numeric: tabular-nums; text-align: right; }
.data-table td.key { color: var(--color-ink); }

/* ============ 筛选 ============ */
.filter-bar { display: flex; flex-wrap: wrap; gap: var(--space-1); margin-bottom: var(--space-4); }
.filter-btn {
  appearance: none;
  padding: 6px 12px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-ink-soft);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .06em;
  cursor: pointer;
  transition: background-color 180ms var(--ease), color 180ms var(--ease), border-color 180ms var(--ease);
}
.filter-btn:hover { background: var(--color-surface-deep); color: var(--color-ink); }
.filter-btn[aria-pressed="true"] {
  background: var(--color-contrast-surface);
  border-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
[data-filter-item][hidden] { display: none; }

/* ============ 旁注 ============ */
.note,
.aside-note {
  padding-left: var(--space-3);
  border-left: var(--border-thin) solid var(--color-line);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  max-width: var(--measure);
}
.aside-note { font-size: var(--text-xs); line-height: 1.9; color: var(--color-ink-muted); }
.note-title {
  display: block;
  margin-bottom: 6px;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .18em;
  color: var(--color-ink-muted);
}

/* ============ 跳转与进度 ============ */
.skip-link {
  position: fixed;
  left: var(--space-2);
  top: -120px;
  z-index: 100;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .08em;
  transition: top 200ms var(--ease);
}
.skip-link:focus { top: var(--space-2); }
.scroll-progress {
  position: fixed;
  top: 0; left: 0;
  z-index: 90;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: width 100ms linear;
}

/* ============ 头部 ============ */
.site-header { position: relative; }
.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: var(--topbar-h);
  padding: 12px clamp(16px, 3vw, 40px);
  background: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.brand { display: inline-flex; align-items: center; gap: 10px; color: inherit; }
.brand-mark {
  position: relative;
  display: grid;
  place-items: center;
  flex: 0 0 auto;
  width: 36px; height: 36px;
  border-radius: var(--radius-sm);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: 1;
}
.brand-mark::after {
  content: "";
  position: absolute;
  left: 5px; right: 5px; bottom: 5px;
  height: 1px;
  background: var(--color-primary);
}
.brand-text { display: flex; flex-direction: column; line-height: 1.16; }
.brand-name { font-family: var(--font-heading); font-size: var(--text-lg); letter-spacing: .06em; color: var(--color-ink); }
.brand-sub { font-family: var(--font-mono); font-size: var(--text-xs); letter-spacing: .16em; color: var(--color-ink-muted); }
.topbar-status { display: flex; align-items: center; gap: var(--space-2); margin: 0; max-width: none; }
.topbar-status-text { font-family: var(--font-mono); font-size: var(--text-xs); letter-spacing: .06em; color: var(--color-ink-muted); }
.topbar-cta { margin-left: auto; }

.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 9px 12px;
  border: 0;
  border-radius: var(--radius-sm);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .12em;
  cursor: pointer;
}
.nav-toggle-bars { position: relative; display: block; width: 16px; height: 1px; background: currentColor; }
.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute; left: 0;
  width: 16px; height: 1px;
  background: currentColor;
  transition: transform 200ms var(--ease), opacity 200ms var(--ease);
}
.nav-toggle-bars::before { top: -5px; }
.nav-toggle-bars::after { top: 5px; }
[data-nav-toggle][aria-expanded="true"] .nav-toggle-bars { background: transparent; }
[data-nav-toggle][aria-expanded="true"] .nav-toggle-bars::before { transform: translateY(5px) rotate(45deg); }
[data-nav-toggle][aria-expanded="true"] .nav-toggle-bars::after { transform: translateY(-5px) rotate(-45deg); }

/* 移动端抽屉（默认态） */
.rail-nav {
  position: fixed;
  top: 0; left: 0;
  z-index: 80;
  width: min(84vw, 320px);
  height: 100vh;
  height: 100dvh;
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  padding: var(--space-8) var(--space-4) var(--space-4);
  background: var(--color-surface-alt);
  border-right: var(--border-thin) solid var(--color-line);
  overflow-y: auto;
  transform: translateX(-102%);
  visibility: hidden;
  transition: transform 240ms var(--ease), visibility 240ms linear;
}
[data-nav][data-open] { transform: translateX(0); visibility: visible; }

.rail-title {
  margin: 0;
  padding-bottom: var(--space-2);
  border-bottom: var(--border-thin) solid var(--color-line);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .4em;
  color: var(--color-ink-muted);
}
.rail-list { position: relative; counter-reset: rail; padding-left: var(--space-3); }
.rail-list::before {
  content: "";
  position: absolute;
  left: 5px; top: 4px; bottom: 4px;
  width: 1px;
  background: var(--color-line);
}
.rail-list li { margin: 0; }
.rail-list a {
  position: relative;
  display: grid;
  grid-template-columns: 2.4em minmax(0, 1fr);
  align-items: baseline;
  gap: 6px;
  padding: 8px 10px 8px 8px;
  border-radius: var(--radius-sm);
  font-family: var(--font-heading);
  font-size: var(--text-sm);
  letter-spacing: .04em;
  color: var(--color-ink-soft);
  transition: background-color 200ms var(--ease), color 200ms var(--ease);
}
.rail-list a::before {
  content: counter(rail, decimal-leading-zero);
  counter-increment: rail;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
  transition: color 200ms var(--ease);
}
.rail-list a::after {
  content: "";
  position: absolute;
  left: -21px; top: 50%;
  width: 6px; height: 6px;
  transform: translateY(-50%);
  background: var(--color-line);
  transition: background-color 200ms var(--ease);
}
.rail-list a:hover { background: var(--color-surface-deep); color: var(--color-ink); }
.rail-list a[aria-current="page"] { background: var(--color-contrast-surface); color: var(--color-contrast-ink); }
.rail-list a[aria-current="page"]::before { color: var(--color-contrast-accent); }
.rail-list a[aria-current="page"]::after { background: var(--color-primary); }

.rail-note {
  margin: auto 0 0;
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-size: var(--text-xs);
  line-height: 1.9;
  color: var(--color-ink-muted);
  max-width: none;
}
.rail-progress {
  margin-top: var(--space-3);
  padding-top: var(--space-2);
  border-top: var(--border-thin) solid var(--color-line);
}
.rail-progress-head {
  display: flex;
  justify-content: space-between;
  gap: var(--space-2);
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .08em;
  color: var(--color-ink-muted);
  max-width: none;
}
.rail-track { display: block; height: 2px; background: var(--color-line); overflow: hidden; }
.rail-fill { display: block; width: 0; height: 100%; background: var(--color-primary); transition: width 100ms linear; }

/* ============ 页脚 ============ */
.site-footer {
  position: relative;
  isolation: isolate;
  margin-top: var(--section-y);
  overflow: hidden;
  border-top: var(--border-thin) solid var(--color-line);
  background: var(--color-surface-alt);
}
.site-footer::before {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: 0;
  height: 200px;
  background: color-mix(in srgb, var(--color-ink) 8%, transparent);
  clip-path: polygon(0% 100%, 0% 64%, 9% 46%, 18% 58%, 28% 30%, 38% 54%, 50% 34%, 61% 58%, 72% 40%, 83% 62%, 92% 48%, 100% 68%, 100% 100%);
  pointer-events: none;
  z-index: 0;
}
.foot-inner { position: relative; z-index: 1; }
.foot-tier { padding-block: var(--space-8); }
.foot-tier + .foot-tier { padding-block: var(--space-6); border-top: var(--border-thin) solid var(--color-line); }
.foot-grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-6) var(--gutter);
}
.foot-brand { grid-column: span 5; }
.brand--foot { margin-bottom: var(--space-3); }
.foot-brand-line { margin: 0 0 var(--space-2); font-size: var(--text-sm); color: var(--color-ink-soft); max-width: 36ch; }
.foot-brand-line--note { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-1); color: var(--color-ink-muted); font-size: var(--text-xs); }
.foot-col { grid-column: span 2; }
.foot-col--wide { grid-column: span 3; }
.foot-col-title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: .2em;
  color: var(--color-ink-muted);
}
.foot-list { display: flex; flex-direction: column; gap: 10px; font-size: var(--text-sm); }
.foot-list a { color: var(--color-ink-soft); transition: color 200ms var(--ease); }
.foot-list a:hover { color: var(--color-accent); }
.foot-legal {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}
.foot-legal-list { display: flex; flex-wrap: wrap; gap: var(--space-4); }
.foot-legal-list a { color: var(--color-ink-soft); transition: color 200ms var(--ease); }
.foot-legal-list a:hover { color: var(--color-accent); }
.foot-icp { margin: 0; font-family: var(--font-mono); font-size: var(--text-xs); letter-spacing: .06em; color: var(--color-ink-muted); }
.foot-copy { margin: 0 0 0 auto; font-family: var(--font-mono); font-size: var(--text-xs); color: var(--color-ink-muted); }
.foot-contact {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-3) var(--gutter);
}
.foot-contact-item { grid-column: span 4; display: flex; flex-direction: column; gap: 4px; }
.foot-contact-label { font-family: var(--font-mono); font-size: var(--text-xs); letter-spacing: .18em; color: var(--color-ink-muted); }
.foot-contact-value { font-size: var(--text-sm); color: var(--color-ink); word-break: break-word; }
.foot-note { margin: var(--space-3) 0 0; font-size: var(--text-xs); line-height: 1.9; color: var(--color-ink-muted); max-width: 62ch; }

/* ============ 桌面：侧边轨道 ============ */
@media (min-width: 1080px) {
  body { padding-left: var(--rail-w); }
  .scroll-progress { left: var(--rail-w); }
  .rail-nav {
    inset: 0 auto 0 0;
    width: var(--rail-w);
    height: 100vh;
    height: 100dvh;
    gap: var(--space-3);
    padding: var(--space-6) var(--space-3) var(--space-4);
    transform: none;
    visibility: visible;
    transition: none;
  }
  .nav-toggle { display: none; }
  .topbar { padding-left: var(--space-6); }
  .foot-tier--legal .container { padding-left: calc(var(--gutter) + var(--space-4)); }
  .foot-tier--contact .container { padding-left: calc(var(--gutter) + var(--space-8)); }
}

/* ============ 平板 ============ */
@media (max-width: 900px) {
  .grid { grid-template-columns: repeat(6, minmax(0, 1fr)); }
  .col-3, .col-4 { grid-column: span 3; }
  .col-5, .col-6, .col-7, .col-8, .col-12 { grid-column: span 6; }
  .split { grid-template-columns: minmax(0, 1fr); gap: var(--space-4); }
  .section { padding-block: var(--space-8); }
  .section--lg { padding-block: var(--section-y); }
  .topbar-status { display: none; }
  .foot-brand { grid-column: span 12; }
  .foot-col, .foot-col--wide { grid-column: span 4; }
  .foot-contact-item { grid-column: span 6; }
}

/* ============ 手机 ============ */
@media (max-width: 600px) {
  .grid { grid-template-columns: repeat(6, minmax(0, 1fr)); }
  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-12 { grid-column: span 6; }
  .section-head { grid-template-columns: minmax(0, 1fr); gap: var(--space-2); align-items: start; }
  .section-num { font-size: var(--text-xl); }
  .topbar { gap: var(--space-2); padding-inline: var(--space-2); }
  .brand-sub { display: none; }
  .btn--sm { padding: 6px 10px; }
  .foot-col, .foot-col--wide { grid-column: span 6; }
  .foot-contact-item { grid-column: span 12; }
  .foot-copy { margin-left: 0; }
  .foot-legal { gap: var(--space-2); }
  .rail-nav { padding: var(--space-6) var(--space-3) var(--space-3); }
}

/* 抽屉打开时的遮罩与滚动锁 */
@media (max-width: 1079px) {
  body.nav-open { overflow: hidden; }
  body.nav-open::after {
    content: "";
    position: fixed;
    inset: 0;
    z-index: 70;
    background: color-mix(in srgb, var(--color-contrast-surface) 58%, transparent);
  }
}

/* ============ 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;
    transition-delay: 0ms !important;
  }
}