:root {
  --color-surface: #fbfbfb;
  --color-surface-alt: #f2f2f2;
  --color-surface-deep: #e5e6e6;
  --color-ink: #414a4e;
  --color-ink-soft: #657176;
  --color-ink-muted: #778388;
  --color-line: #dadbdc;
  --color-primary: #3a7d9c;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e0e9ee;
  --color-accent: #20836e;
  --color-accent-ink: #ffffff;
  --color-highlight: #d4e5e2;
  --color-focus: #167e68;
  --color-contrast-surface: #101518;
  --color-contrast-ink: #e4e6e7;
  --color-contrast-line: #3f4346;
  --color-contrast-accent: #32cdac;
  --overlay-scrim: linear-gradient(180deg, rgba(16, 21, 24, 0.35) 0%, rgba(16, 21, 24, 0.72) 55%, rgba(16, 21, 24, 0.92) 100%);
  --font-heading: "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --text-xs: 12.2px;
  --text-sm: 15.2px;
  --text-base: 17px;
  --text-lg: 21.2px;
  --text-xl: 26.6px;
  --text-2xl: 33.2px;
  --text-3xl: 41.5px;
  --text-4xl: 51.9px;
  --text-display: clamp(36px, 7.3vw, 94px);
  --text-figure: clamp(30px, 5.3vw, 68px);
  --weight-heading: 699;
  --weight-body: 400;
  --leading-body: 1.71;
  --leading-heading: 1.23;
  --tracking-heading: 0.002em;
  --radius-sm: 6px;
  --radius-md: 9px;
  --radius-lg: 12px;
  --radius-pill: 999px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: 0 6px 18px rgba(65, 74, 78, 0.08);
  --shadow-2: 0 18px 44px rgba(65, 74, 78, 0.14);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1160px;
  --measure: 73ch;
  --gutter: 32px;
  --section-y: 82px;
  --section-y-lg: 115px;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: var(--space-8);
}

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);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, svg, video, canvas { display: block; max-width: 100%; }
img { height: auto; }
button { font: inherit; cursor: pointer; }
a { color: var(--color-primary); text-decoration: none; }
a:hover { color: var(--color-accent); text-decoration: underline; text-underline-offset: 3px; }

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

/* ============ 中文排版 ============ */
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);
  text-wrap: balance;
}
h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }

p { margin: 0 0 var(--space-2); text-wrap: pretty; }
strong, b { font-weight: var(--weight-heading); }
small { font-size: var(--text-xs); color: var(--color-ink-muted); }
code, kbd, samp { font-family: var(--font-mono); font-size: 0.94em; }

/* ============ 布局工具 ============ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}

.section { padding-block: var(--section-y); }
.section--lg { padding-block: var(--section-y-lg); }
.section--alt { background-color: var(--color-surface-alt); }
.section--deep { background-color: var(--color-surface-deep); }
.section--contrast {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.section--contrast h1,
.section--contrast h2,
.section--contrast h3,
.section--contrast h4 { color: var(--color-contrast-ink); }
.section--contrast p { color: color-mix(in srgb, var(--color-contrast-ink) 84%, transparent); }
.section--contrast a { color: var(--color-contrast-accent); }
.section--contrast .panel {
  background-color: color-mix(in srgb, var(--color-contrast-ink) 6%, var(--color-contrast-surface));
  border-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
  box-shadow: none;
}

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

.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;
}

/* ============ 文字组件 ============ */
.prose { max-width: var(--measure); }
.prose p { margin-bottom: var(--space-3); }
.prose ul, .prose ol { margin: 0 0 var(--space-3); padding-left: var(--space-3); }
.prose li { margin-bottom: var(--space-1); }

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

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  margin-bottom: var(--space-2);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}
.eyebrow::before {
  content: "";
  width: 22px;
  height: 2px;
  border-radius: var(--radius-pill);
  background-color: var(--color-accent);
  flex: none;
}
.section--contrast .eyebrow { color: color-mix(in srgb, var(--color-contrast-ink) 72%, transparent); }
.section--contrast .eyebrow::before { background-color: var(--color-contrast-accent); }

.rule {
  height: 2px;
  width: 100%;
  border: 0;
  margin: var(--space-4) 0;
  border-radius: var(--radius-pill);
  background-color: var(--color-accent);
  opacity: 0.6;
}
.section--contrast .rule,
.rule--bright {
  background-color: var(--color-contrast-accent);
  opacity: 1;
}

.figure-num {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}
.section--contrast .figure-num { color: var(--color-contrast-accent); }

/* ============ 框体 / 标签 / 图例 ============ */
.panel {
  padding: var(--space-3);
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-1);
}
.panel--inset {
  background-color: var(--color-surface-deep);
  box-shadow: none;
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 3px 10px;
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  background-color: var(--color-primary-soft);
  color: var(--color-primary);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  line-height: 1.5;
}
.tag--accent {
  background-color: var(--color-highlight);
  color: var(--color-accent);
}
.tag--line {
  background-color: transparent;
  border-color: var(--color-line);
  color: var(--color-ink-muted);
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-3);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}
.legend__item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.legend__swatch {
  width: 10px;
  height: 10px;
  flex: none;
  border-radius: 3px;
  background-color: var(--color-primary);
}
.legend__swatch--accent { background-color: var(--color-accent); }
.legend__swatch--deep { background-color: var(--color-contrast-surface); }
.legend__swatch--line {
  background-color: transparent;
  border: var(--border-thin) solid var(--color-line);
}
.section--contrast .legend { color: color-mix(in srgb, var(--color-contrast-ink) 70%, transparent); }
.section--contrast .legend__swatch { background-color: var(--color-contrast-accent); }

/* ============ 面包屑 ============ */
.breadcrumbs {
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}
.breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.breadcrumbs li { display: inline-flex; align-items: center; }
.breadcrumbs li + li::before {
  content: "/";
  margin: 0 var(--space-1);
  color: var(--color-line);
}
.breadcrumbs a { color: var(--color-ink-soft); }
.breadcrumbs a:hover { color: var(--color-accent); }
.breadcrumbs [aria-current="page"] { color: var(--color-ink); }

/* ============ 按钮 ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 11px 22px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: 0.02em;
  text-decoration: none;
  transition: background-color 150ms ease, border-color 150ms ease, color 150ms ease, box-shadow 150ms ease;
}
.btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  text-decoration: none;
}
.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) 84%, var(--color-contrast-surface));
  border-color: color-mix(in srgb, var(--color-primary) 84%, var(--color-contrast-surface));
  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-contrast-surface));
  border-color: color-mix(in srgb, var(--color-accent) 84%, var(--color-contrast-surface));
  color: var(--color-accent-ink);
}
.btn--quiet {
  padding-inline: 4px;
  background-color: transparent;
  border-color: transparent;
  color: var(--color-primary);
}
.btn--quiet:hover { color: var(--color-accent); }

/* ============ 图像容器（页面阶段复用） ============ */
.media {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-lg);
  background-color: var(--color-contrast-surface);
  isolation: isolate;
}
.media--21x9 { aspect-ratio: 21 / 9; }
.media--16x9 { aspect-ratio: 16 / 9; }
.media--1x1 { aspect-ratio: 1 / 1; }
.media__img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.media__scrim {
  position: absolute;
  inset: 0;
  background-image: var(--overlay-scrim);
  pointer-events: none;
  z-index: 1;
}
.media__body {
  position: absolute;
  left: var(--space-3);
  right: var(--space-3);
  bottom: var(--space-3);
  z-index: 2;
  color: var(--color-contrast-ink);
}
.media__body h2,
.media__body h3 { color: var(--color-contrast-ink); margin-bottom: var(--space-1); }
.media__body p {
  margin: 0;
  font-size: var(--text-sm);
  color: color-mix(in srgb, var(--color-contrast-ink) 82%, transparent);
}

/* ============ 头部 ============ */
.site-header {
  position: relative;
  z-index: 40;
  background-color: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.site-header__inner {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-3);
  max-width: var(--container);
  margin-inline: auto;
  padding: var(--space-3) var(--space-3) var(--space-2);
}

.skip-link {
  position: absolute;
  left: var(--space-2);
  top: -120px;
  z-index: 100;
  padding: 10px 18px;
  border-radius: var(--radius-md);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  text-decoration: none;
  transition: top 140ms ease;
}
.skip-link:focus {
  top: var(--space-2);
  color: var(--color-contrast-ink);
  text-decoration: none;
}

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 0;
  height: 3px;
  z-index: 90;
  background-color: var(--color-contrast-accent);
  pointer-events: none;
  transition: width 120ms linear;
}

.site-header__utility {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-1) var(--space-3);
  margin: 0;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
}
.site-header__utility a {
  color: var(--color-ink-muted);
  border-bottom: var(--border-thin) solid transparent;
  transition: color 150ms ease, border-color 150ms ease;
}
.site-header__utility a:hover {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
  text-decoration: none;
}

.masthead { text-align: center; }
.masthead__brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  color: var(--color-ink);
}
.masthead__brand:hover { color: var(--color-ink); text-decoration: none; }
.masthead__mark {
  width: 10px;
  height: 10px;
  flex: none;
  border-radius: 3px;
  background-color: var(--color-accent);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--color-accent) 16%, transparent);
}
.masthead__name {
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  letter-spacing: 0.02em;
  line-height: var(--leading-heading);
}
.masthead__tagline {
  margin: var(--space-1) 0 0;
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-muted);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 9px 18px;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  background-color: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  transition: background-color 150ms ease, border-color 150ms ease, color 150ms ease;
}
.nav-toggle__bars {
  position: relative;
  display: inline-block;
  width: 16px;
  height: 2px;
  border-radius: var(--radius-pill);
  background-color: currentColor;
}
.nav-toggle__bars::before,
.nav-toggle__bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 16px;
  height: 2px;
  border-radius: var(--radius-pill);
  background-color: currentColor;
  transition: transform 160ms ease, top 160ms ease;
}
.nav-toggle__bars::before { top: -5px; }
.nav-toggle__bars::after { top: 5px; }
.nav-toggle[aria-expanded="true"] {
  border-color: var(--color-accent);
  background-color: var(--color-highlight);
  color: var(--color-accent);
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bars { background-color: transparent; }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars::before { top: 0; transform: rotate(45deg); }
.nav-toggle[aria-expanded="true"] .nav-toggle__bars::after { top: 0; transform: rotate(-45deg); }

.site-nav { width: 100%; }
.site-nav__list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-1) var(--space-3);
  margin: 0;
  padding: 0;
  list-style: none;
}
.site-nav__list a {
  position: relative;
  display: inline-block;
  padding: var(--space-1) 2px;
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  letter-spacing: 0.04em;
  transition: color 150ms ease;
}
.site-nav__list a::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 2px;
  border-radius: var(--radius-pill);
  background-color: var(--color-accent);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 160ms ease;
}
.site-nav__list a:hover {
  color: var(--color-ink);
  text-decoration: none;
}
.site-nav__list a:hover::after { transform: scaleX(1); }
.site-nav__list a[aria-current="page"] {
  color: var(--color-accent);
  font-weight: var(--weight-heading);
}
.site-nav__list a[aria-current="page"]::after { transform: scaleX(1); }

/* ============ 页脚 ============ */
.site-footer {
  background-color: var(--color-surface-alt);
  border-top: var(--border-thin) solid var(--color-line);
  padding-block: var(--section-y) var(--space-6);
}
.site-footer__inner {
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--space-3);
}
.site-footer__lead {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-2) var(--space-4);
  padding-bottom: var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.site-footer__brand {
  margin: 0;
  font-family: var(--font-heading);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
  letter-spacing: 0.02em;
}
.site-footer__routes {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1) var(--space-3);
  margin-left: auto;
}
.site-footer__routes a {
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  border-bottom: var(--border-thin) solid transparent;
  transition: color 150ms ease, border-color 150ms ease;
}
.site-footer__routes a:hover {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
  text-decoration: none;
}
.site-footer__panels {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2);
  margin-top: var(--space-4);
}
.footer-panel {
  padding: var(--space-3);
  background-color: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-1);
}
.footer-panel__title {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  margin: 0 0 var(--space-2);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: 0.1em;
  color: var(--color-ink);
}
.footer-panel__index {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--color-accent);
  font-variant-numeric: tabular-nums;
}
.footer-panel__title::after {
  content: "";
  flex: 1;
  height: 2px;
  border-radius: var(--radius-pill);
  background-color: var(--color-accent);
  opacity: 0.45;
}
.footer-panel__body {
  margin: 0;
  font-size: var(--text-sm);
  line-height: 1.75;
  color: var(--color-ink-soft);
}
.site-footer__legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-2);
  margin-top: var(--space-4);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}
.site-footer__dot {
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background-color: var(--color-accent);
}

/* ============ 显现动效 ============ */
[data-reveal] {
  transition: opacity 180ms ease-out, transform 180ms ease-out;
}
html.js-ready [data-reveal]:not(.is-revealed) {
  opacity: 0;
  transform: translateY(14px);
}

/* ============ 响应式 ============ */
@media (min-width: 768px) {
  .container,
  .site-header__inner,
  .site-footer__inner { padding-inline: var(--gutter); }
  .site-footer__panels { gap: var(--space-3); }
}

@media (min-width: 640px) {
  .site-footer__panels { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (min-width: 1024px) {
  .site-footer__panels {
    grid-template-columns: 5fr 4fr 3fr;
    gap: var(--space-3);
  }
}

@media (min-width: 861px) {
  .site-header__inner {
    gap: var(--space-3);
    padding-block: var(--space-4) var(--space-3);
  }
  .masthead__name { font-size: var(--text-xl); }
  .site-header__utility {
    position: absolute;
    right: var(--gutter);
    top: var(--space-4);
    justify-content: flex-end;
  }
}

@media (max-width: 860px) {
  .nav-toggle { display: inline-flex; }
  .site-nav {
    display: none;
    width: 100%;
    padding-top: var(--space-2);
    border-top: var(--border-thin) solid var(--color-line);
  }
  .site-nav[data-open] { display: block; }
  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
  }
  .site-nav__list li + li { border-top: var(--border-thin) solid var(--color-line); }
  .site-nav__list a {
    display: block;
    width: 100%;
    padding: var(--space-2) var(--space-1);
    font-size: var(--text-base);
  }
  .site-nav__list a::after { display: none; }
  .site-nav__list a[aria-current="page"] {
    padding-inline: var(--space-2);
    background-color: var(--color-highlight);
    border-radius: var(--radius-sm);
  }
  .site-footer__routes { margin-left: 0; }
}

@media (max-width: 599px) {
  .section { padding-block: var(--space-6); }
  .section--lg { padding-block: var(--space-8); }
  .masthead__name { font-size: var(--text-base); }
  .masthead__tagline { letter-spacing: 0.08em; }
}

/* ============ 可访问性 ============ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .scroll-progress { transition: none; }
  html.js-ready [data-reveal],
  html.js-ready [data-reveal]:not(.is-revealed) {
    opacity: 1 !important;
    transform: none !important;
  }
}