:root {
  --color-surface: #232125;
  --color-surface-alt: #312f34;
  --color-surface-deep: #434046;
  --color-ink: #c2bbc9;
  --color-ink-soft: #978ba2;
  --color-ink-muted: #80738c;
  --color-line: #403d43;
  --color-primary: #964dd6;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #33273e;
  --color-accent: #34cb38;
  --color-accent-ink: #151118;
  --color-highlight: #264028;
  --color-focus: #28d72c;
  --color-contrast-surface: #efeef0;
  --color-contrast-ink: #333036;
  --color-contrast-line: #c6c4c7;
  --color-contrast-accent: #1f7a22;
  --overlay-scrim: linear-gradient(180deg, rgba(239, 238, 240, 0.35) 0%, rgba(239, 238, 240, 0.72) 55%, rgba(239, 238, 240, 0.92) 100%);
  --font-heading: STZhongsong, "Source Han Serif SC", "Songti SC", SimSun, serif;
  --font-body: "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 10.4px;
  --text-sm: 13.9px;
  --text-base: 16px;
  --text-lg: 21.3px;
  --text-xl: 28.4px;
  --text-2xl: 37.9px;
  --text-3xl: 50.5px;
  --text-4xl: 67.3px;
  --text-display: clamp(53px, 10.9vw, 140px);
  --text-figure: clamp(44px, 7.9vw, 101px);
  --weight-heading: 570;
  --weight-body: 400;
  --leading-body: 1.74;
  --leading-heading: 1.29;
  --tracking-heading: 0.027em;
  --radius-sm: 7px;
  --radius-md: 9px;
  --radius-lg: 11px;
  --radius-pill: 999px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: 0 6px 18px rgba(194, 187, 201, 0.08);
  --shadow-2: 0 18px 44px rgba(194, 187, 201, 0.14);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1200px;
  --measure: 62ch;
  --gutter: 16px;
  --section-y: 110px;
  --section-y-lg: 154px;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 108px;
}

body {
  margin: 0;
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-base);
  font-weight: var(--weight-body);
  line-height: var(--leading-body);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

img, svg, video, canvas { display: block; max-width: 100%; height: auto; }
button, input, select, textarea { font: inherit; color: inherit; }
ul, ol { margin: 0; padding: 0; list-style: none; }
h1, h2, h3, h4, h5, h6, p, figure, blockquote { margin: 0; }
table { border-collapse: collapse; width: 100%; }

/* ============================================================
   2. 中文排版基线
   ============================================================ */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  text-wrap: pretty;
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }
h5, h6 { font-size: var(--text-base); }

p { text-wrap: pretty; }

a {
  color: var(--color-accent);
  text-decoration-line: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  text-decoration-color: color-mix(in srgb, var(--color-accent) 42%, transparent);
  transition: color 160ms ease-out, text-decoration-color 160ms ease-out;
}

a:hover { color: color-mix(in srgb, var(--color-accent) 72%, var(--color-primary-ink)); }

strong, b { font-weight: var(--weight-heading); color: color-mix(in srgb, var(--color-ink) 74%, var(--color-primary-ink)); }

::selection {
  background: var(--color-highlight);
  color: color-mix(in srgb, var(--color-ink) 60%, var(--color-primary-ink));
}

:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ============================================================
   3. 容器与栅格
   ============================================================ */
.container {
  width: min(100% - (var(--space-2) * 2), var(--container));
  margin-inline: auto;
}

.container-narrow {
  width: min(100% - (var(--space-2) * 2), 860px);
  margin-inline: auto;
}

.grid {
  display: grid;
  gap: var(--gutter);
  grid-template-columns: repeat(12, minmax(0, 1fr));
}

.grid-split { grid-template-columns: repeat(12, minmax(0, 1fr)); }
.grid-split > .col-head { grid-column: span 4; }
.grid-split > .col-body { grid-column: span 7; }
.grid-split > .col-aside { grid-column: span 1; }

.grid-cards { grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }

.stack > * + * { margin-top: var(--space-2); }
.cluster { display: flex; flex-wrap: wrap; gap: var(--space-1); align-items: center; }

/* ============================================================
   4. 金属细边 / 卡片 / 浅色托起块
   ============================================================ */
.metal-edge { position: relative; }

.metal-edge::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  padding: var(--border-thin);
  background: linear-gradient(
    142deg,
    color-mix(in srgb, var(--color-primary) 62%, transparent) 0%,
    color-mix(in srgb, var(--color-line) 88%, transparent) 30%,
    color-mix(in srgb, var(--color-line) 96%, transparent) 66%,
    color-mix(in srgb, var(--color-accent) 26%, transparent) 100%
  );
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  mask-composite: exclude;
  pointer-events: none;
}

.surface-card {
  position: relative;
  background-color: var(--color-surface-alt);
  border-radius: var(--radius-lg);
  padding: var(--space-3);
  box-shadow: var(--shadow-1);
  transition: transform 160ms ease-out, box-shadow 160ms ease-out, background-color 160ms ease-out;
}

.surface-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-2);
  background-color: color-mix(in srgb, var(--color-surface-alt) 88%, var(--color-surface-deep));
}

.contrast-block {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
}

.contrast-block h1,
.contrast-block h2,
.contrast-block h3,
.contrast-block h4 { color: var(--color-contrast-ink); }

.contrast-block p { color: var(--color-contrast-ink); }
.contrast-block a { color: var(--color-contrast-accent); text-decoration-color: color-mix(in srgb, var(--color-contrast-accent) 45%, transparent); }
.contrast-block .num { color: var(--color-contrast-accent); }

/* ============================================================
   5. 区块节奏与刻度分隔
   ============================================================ */
.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--tight { padding-block: var(--space-6); }

.section--alt {
  background-color: var(--color-surface-alt);
  border-radius: var(--radius-lg);
}

.tick-rule {
  height: 9px;
  background-image:
    repeating-linear-gradient(90deg, var(--color-line) 0 1px, transparent 1px 22px),
    repeating-linear-gradient(90deg, color-mix(in srgb, var(--color-line) 70%, transparent) 0 1px, transparent 1px 6px);
  background-size: 100% 6px, 100% 3px;
  background-position: 0 0, 0 100%;
  background-repeat: repeat-x, repeat-x;
}

.section-head {
  display: grid;
  grid-template-columns: 4fr 7fr 1fr;
  gap: var(--gutter);
  align-items: end;
  margin-bottom: var(--space-4);
}

.section-num {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-3xl);
  line-height: 0.9;
  letter-spacing: 0.02em;
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

.section-title {
  font-family: var(--font-heading);
  font-size: var(--text-2xl);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.section-aside {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-muted);
  justify-self: end;
  writing-mode: horizontal-tb;
}

/* ============================================================
   6. 文字工具与展示型组件
   ============================================================ */
.num,
.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.06em;
}

.muted { color: var(--color-ink-muted); }
.soft { color: var(--color-ink-soft); }

.lead {
  font-size: var(--text-lg);
  line-height: 1.6;
  color: var(--color-ink);
  max-width: var(--measure);
}

.title-display {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  line-height: 1.02;
  letter-spacing: 0.012em;
  color: color-mix(in srgb, var(--color-ink) 76%, var(--color-primary-ink));
  text-wrap: balance;
}

.figure-value {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 0.9;
  letter-spacing: -0.01em;
  color: var(--color-accent);
  font-variant-numeric: tabular-nums;
}

.prose {
  max-width: var(--measure);
  color: var(--color-ink);
}

.prose > * + * { margin-top: var(--space-3); }
.prose h2 { font-size: var(--text-xl); margin-top: var(--space-6); }
.prose h3 { font-size: var(--text-lg); margin-top: var(--space-4); }
.prose ul, .prose ol { list-style: none; }
.prose li {
  padding-left: var(--space-3);
  position: relative;
}
.prose li + li { margin-top: var(--space-1); }
.prose li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--color-primary);
}
.prose blockquote {
  border-left: 2px solid var(--color-accent);
  padding-left: var(--space-3);
  color: var(--color-ink-soft);
}

/* ============================================================
   7. 按钮
   ============================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 12px 22px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: transparent;
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 160ms ease-out, border-color 160ms ease-out, color 160ms ease-out, transform 160ms ease-out;
}

.btn:hover { border-color: var(--color-accent); color: var(--color-accent); }
.btn:active { transform: translateY(1px); }

.btn--primary {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}
.btn--primary:hover {
  background-color: color-mix(in srgb, var(--color-primary) 78%, var(--color-primary-ink));
  border-color: color-mix(in srgb, var(--color-primary) 78%, var(--color-primary-ink));
  color: var(--color-primary-ink);
}

.btn--accent {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}
.btn--accent:hover {
  background-color: color-mix(in srgb, var(--color-accent) 84%, var(--color-primary-ink));
  border-color: color-mix(in srgb, var(--color-accent) 84%, var(--color-primary-ink));
  color: var(--color-accent-ink);
}

.btn--ghost { background-color: var(--color-surface-deep); }

/* ============================================================
   8. 标签 / 筛选 chip / 面包屑
   ============================================================ */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: color-mix(in srgb, var(--tag-color, var(--color-primary)) 16%, var(--color-surface-deep));
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  white-space: nowrap;
}

.tag::before {
  content: "";
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background-color: var(--tag-color, var(--color-primary));
  flex: none;
}

.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: var(--color-surface-deep);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: border-color 160ms ease-out, background-color 160ms ease-out, color 160ms ease-out;
}

.chip:hover { color: var(--color-ink); border-color: color-mix(in srgb, var(--color-accent) 55%, var(--color-line)); }

.chip[data-active="true"],
.chip[aria-pressed="true"] {
  background-color: var(--color-highlight);
  border-color: var(--color-accent);
  color: color-mix(in srgb, var(--color-ink) 70%, var(--color-primary-ink));
}

.crumbs {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding-block: var(--space-3);
}

.crumbs a { color: var(--color-ink-soft); text-decoration: none; }
.crumbs a:hover { color: var(--color-accent); }
.crumbs .sep { color: var(--color-line); }
.crumbs [aria-current="page"] { color: var(--color-ink); }

/* ============================================================
   9. 条目流 / 步骤 / 面板 / 分段切换
   ============================================================ */
.entry-list { display: grid; gap: 2px; }

.entry {
  display: grid;
  grid-template-columns: 64px 1fr auto;
  gap: var(--space-3);
  align-items: baseline;
  padding: var(--space-3);
  border-radius: var(--radius-md);
  background-color: var(--color-surface-alt);
  text-decoration: none;
  color: inherit;
  transition: background-color 160ms ease-out, transform 160ms ease-out;
}

.entry:hover {
  background-color: color-mix(in srgb, var(--color-surface-alt) 78%, var(--color-surface-deep));
  transform: translateX(2px);
}

.entry-idx {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
  letter-spacing: 0.08em;
}

.entry-title {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  color: var(--color-ink);
  letter-spacing: var(--tracking-heading);
}

.entry-desc {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  margin-top: 4px;
  max-width: var(--measure);
}

.steps { display: grid; gap: var(--space-3); counter-reset: step; }

.step {
  position: relative;
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: var(--space-3);
  padding: var(--space-3) 0;
  padding-left: 0;
}

.step::before {
  content: "";
  position: absolute;
  left: 43px;
  top: 0;
  bottom: 0;
  width: 1px;
  background-color: var(--color-line);
}

.step-mark {
  position: relative;
  z-index: 1;
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  border-radius: var(--radius-pill);
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
}

.step-body { padding-block: var(--space-1); }

.panel {
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  background-color: var(--color-surface-alt);
  overflow: hidden;
}

.panel + .panel { margin-top: var(--space-2); }

.panel-trigger {
  display: flex;
  width: 100%;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  padding: var(--space-3);
  border: 0;
  background: transparent;
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  letter-spacing: var(--tracking-heading);
  text-align: left;
  cursor: pointer;
}

.panel-trigger:hover { color: color-mix(in srgb, var(--color-ink) 70%, var(--color-primary-ink)); }

.panel-state {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-accent);
  flex: none;
}

.panel-body {
  padding: 0 var(--space-3) var(--space-3);
  max-width: var(--measure);
  color: var(--color-ink-soft);
}

.panel-body[hidden] { display: none; }

.tabs { display: grid; gap: var(--space-3); }

.tab-list {
  display: flex;
  flex-wrap: wrap;
  gap: 2px;
  padding: 4px;
  border-radius: var(--radius-pill);
  background-color: var(--color-surface-deep);
  width: fit-content;
  max-width: 100%;
}

.tab {
  padding: 8px 18px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  background: transparent;
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  cursor: pointer;
  transition: background-color 160ms ease-out, color 160ms ease-out, border-color 160ms ease-out;
}

.tab:hover { color: var(--color-ink); }

.tab[aria-selected="true"] {
  background-color: color-mix(in srgb, var(--color-accent) 16%, var(--color-surface-alt));
  border-color: var(--color-accent);
  color: color-mix(in srgb, var(--color-ink) 70%, var(--color-primary-ink));
}

.tab-panel[hidden] { display: none; }

/* ============================================================
   10. 图片容器基础规则
   ============================================================ */
.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-lg);
  background-color: var(--color-surface-deep);
  isolation: isolate;
}

.media img {
  width: 100%;
  height: 100%;
  min-height: 180px;
  object-fit: cover;
}

.media::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
  z-index: 1;
  pointer-events: none;
}

.media-caption {
  position: absolute;
  inset-inline: 0;
  bottom: 0;
  z-index: 2;
  padding: var(--space-3);
  color: var(--color-contrast-ink);
}

.media-caption h3,
.media-caption p { color: var(--color-contrast-ink); }
.media-caption .num { color: var(--color-contrast-accent); }

.media--tall img { min-height: 320px; }
.media--wide img { min-height: 220px; }

/* ============================================================
   11. 显现动效
   ============================================================ */
[data-reveal] {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 320ms ease-out, transform 320ms ease-out;
}

[data-reveal][data-revealed="true"] {
  opacity: 1;
  transform: none;
}

/* ============================================================
   12. 头部
   ============================================================ */
.skip-link {
  position: fixed;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 400;
  padding: 10px 20px;
  border-radius: var(--radius-pill);
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  text-decoration: none;
  transform: translateY(-220%);
  transition: transform 160ms ease-out;
}

.skip-link:focus { transform: none; color: var(--color-accent-ink); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 120;
  padding: var(--space-3) 0 var(--space-2);
  background-color: var(--color-surface);
  transition: padding 220ms ease-out;
}

.site-header[data-stuck="true"] {
  padding-top: var(--space-1);
  padding-bottom: var(--space-1);
}

.nav-capsule {
  position: relative;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-2) var(--space-2) var(--space-3);
  border-radius: var(--radius-pill);
  background-color: var(--color-surface-alt);
  box-shadow: var(--shadow-1);
  transition: padding 220ms ease-out, box-shadow 220ms ease-out;
}

.site-header[data-stuck="true"] .nav-capsule {
  padding-block: var(--space-1);
  box-shadow: var(--shadow-2);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex: none;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  flex: none;
  border-radius: var(--radius-md);
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  line-height: 1;
}

.brand-text { display: block; min-width: 0; }

.brand-name {
  display: block;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  letter-spacing: var(--tracking-heading);
  line-height: 1.15;
  color: var(--color-ink);
}

.brand-tagline {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
  white-space: nowrap;
}

.nav {
  margin-inline: auto;
  min-width: 0;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-wrap: nowrap;
}

.nav-list a {
  position: relative;
  display: block;
  padding: 8px 14px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  text-decoration: none;
  white-space: nowrap;
  transition: color 160ms ease-out, border-color 160ms ease-out, background-color 160ms ease-out, font-size 220ms ease-out;
}

.nav-list a:hover {
  color: var(--color-ink);
  border-color: var(--color-line);
}

.nav-list a[aria-current="page"] {
  color: color-mix(in srgb, var(--color-ink) 68%, var(--color-primary-ink));
  background-color: color-mix(in srgb, var(--color-accent) 14%, var(--color-surface-deep));
  border-color: var(--color-accent);
}

.nav-list a[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 1px;
  width: 22px;
  height: 2px;
  border-radius: 1px;
  background-color: var(--color-accent);
  transform: translateX(-50%);
}

.site-header[data-stuck="true"] .nav-list a {
  font-size: calc(var(--text-sm) * 0.92);
  padding: 6px 12px;
}

.nav-cta {
  flex: none;
  display: inline-flex;
  align-items: center;
  padding: 9px 18px;
  border-radius: var(--radius-pill);
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  text-decoration: none;
  transition: background-color 160ms ease-out;
}

.nav-cta:hover {
  background-color: color-mix(in srgb, var(--color-primary) 76%, var(--color-primary-ink));
  color: var(--color-primary-ink);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 8px 14px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: var(--color-surface-deep);
  color: var(--color-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  cursor: pointer;
  flex: none;
}

.nav-toggle:hover { border-color: var(--color-accent); }

.nav-toggle-bars {
  position: relative;
  display: block;
  width: 14px;
  height: 2px;
  border-radius: 2px;
  background-color: currentColor;
}

.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 14px;
  height: 2px;
  border-radius: 2px;
  background-color: currentColor;
  transition: transform 220ms ease-out;
}

.nav-toggle-bars::before { top: -5px; }
.nav-toggle-bars::after { top: 5px; }

.nav-toggle[aria-expanded="true"] .nav-toggle-bars { background-color: transparent; }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars::before { transform: translateY(5px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle-bars::after { transform: translateY(-5px) rotate(-45deg); }

.nav-toggle-label { white-space: nowrap; }

/* ============================================================
   13. 页脚
   ============================================================ */
.site-footer {
  margin-top: var(--section-y);
  padding-bottom: var(--space-4);
  background-color: var(--color-surface-alt);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
}

.site-footer .tick-rule { margin-bottom: var(--space-6); }

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1.4fr;
  gap: var(--space-6) var(--space-4);
  padding-bottom: var(--space-6);
}

.footer-brand-name {
  font-family: var(--font-heading);
  font-size: var(--text-xl);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.footer-brand-note {
  margin-top: var(--space-2);
  max-width: 34ch;
  color: var(--color-ink-soft);
  line-height: 1.7;
}

.footer-entry {
  margin-top: var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-accent);
}

.footer-col-title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-body);
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
  text-transform: uppercase;
}

.footer-col-title::after {
  content: "";
  display: block;
  margin-top: var(--space-1);
  height: 4px;
  background-image: repeating-linear-gradient(90deg, var(--color-line) 0 1px, transparent 1px 6px);
}

.footer-links {
  margin-top: var(--space-3);
  display: grid;
  gap: 7px;
}

.footer-links a {
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  text-decoration: none;
  transition: color 160ms ease-out;
}

.footer-links a:hover { color: var(--color-accent); }

.footer-links--plain li {
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  line-height: 1.65;
  overflow-wrap: anywhere;
}

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.footer-note { color: var(--color-ink-muted); }

/* ============================================================
   14. 响应式
   ============================================================ */
@media (max-width: 1080px) {
  .footer-grid { grid-template-columns: 1.4fr 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
}

@media (max-width: 920px) {
  :root { --section-y: 76px; --section-y-lg: 96px; }

  .section-head { grid-template-columns: 1fr; gap: var(--space-1); }
  .section-num { font-size: var(--text-2xl); }
  .section-aside { justify-self: start; }

  .grid-split > .col-head,
  .grid-split > .col-body,
  .grid-split > .col-aside { grid-column: 1 / -1; }

  .nav-toggle { display: inline-flex; }

  .nav {
    position: absolute;
    top: calc(100% + var(--space-1));
    left: 0;
    right: 0;
    margin: 0;
    display: none;
    padding: var(--space-2);
    border: var(--border-thin) solid var(--color-line);
    border-radius: var(--radius-lg);
    background-color: var(--color-surface-alt);
    box-shadow: var(--shadow-2);
    max-height: min(70vh, 520px);
    overflow-y: auto;
  }

  .nav-capsule[data-open="true"] .nav { display: block; }

  .nav-list { flex-direction: column; align-items: stretch; gap: 2px; }

  .nav-list a {
    padding: 12px 14px;
    border-radius: var(--radius-md);
    font-size: var(--text-base);
  }

  .nav-list a[aria-current="page"]::after {
    left: 0;
    top: 50%;
    bottom: auto;
    width: 3px;
    height: 18px;
    margin-top: -9px;
    transform: none;
  }

  .site-header[data-stuck="true"] .nav-list a { font-size: var(--text-base); padding: 12px 14px; }

  .brand-text { display: none; }
  .nav-cta { margin-left: auto; padding: 8px 14px; font-size: var(--text-xs); }

  .entry { grid-template-columns: 48px 1fr; }
  .entry > :last-child { grid-column: 2; }

  .step { grid-template-columns: 60px 1fr; }
  .step::before { left: 29px; }
}

@media (max-width: 620px) {
  .footer-grid { grid-template-columns: 1fr; gap: var(--space-4); }
  .footer-bottom { flex-direction: column; align-items: flex-start; }

  .brand { gap: var(--space-1); }
  .brand-mark { width: 34px; height: 34px; font-size: var(--text-base); }
  .nav-toggle-label { display: none; }
  .nav-capsule { padding-left: var(--space-2); }

  .prose li { padding-left: var(--space-2); }
  .contrast-block { padding: var(--space-3); }

  .tab-list { width: 100%; }
  .tab { flex: 1 1 auto; text-align: center; padding: 8px 10px; }
}

/* ============================================================
   15. 降低动效
   ============================================================ */
@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;
  }

  [data-reveal] {
    opacity: 1;
    transform: none;
  }

  .surface-card:hover,
  .entry:hover { transform: none; }
}