:root {
  --color-surface: #fbfbfb;
  --color-surface-alt: #f2f2f2;
  --color-surface-deep: #e5e6e6;
  --color-ink: #444a50;
  --color-ink-soft: #687078;
  --color-ink-muted: #777f88;
  --color-line: #dadbdc;
  --color-primary: #4d79a8;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e3e9ef;
  --color-accent: #318186;
  --color-accent-ink: #ffffff;
  --color-highlight: #d7e5e6;
  --color-focus: #257e84;
  --color-contrast-surface: #1b2126;
  --color-contrast-ink: #e4e5e7;
  --color-contrast-line: #474c50;
  --color-contrast-accent: #44b3bb;
  --overlay-scrim: linear-gradient(180deg, rgba(27, 33, 38, 0.35) 0%, rgba(27, 33, 38, 0.72) 55%, rgba(27, 33, 38, 0.92) 100%);
  --font-heading: "Hiragino Sans GB", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "Hiragino Sans GB", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, Menlo, Consolas, monospace;
  --text-xs: 13.7px;
  --text-sm: 16.4px;
  --text-base: 18px;
  --text-lg: 21.6px;
  --text-xl: 25.9px;
  --text-2xl: 31.1px;
  --text-3xl: 37.3px;
  --text-4xl: 44.8px;
  --text-display: clamp(34px, 6.5vw, 83px);
  --text-figure: clamp(28px, 4.7vw, 60px);
  --weight-heading: 678;
  --weight-body: 400;
  --leading-body: 1.79;
  --leading-heading: 1.28;
  --tracking-heading: -0.009em;
  --radius-sm: 18px;
  --radius-md: 20px;
  --radius-lg: 22px;
  --radius-pill: 999px;
  --border-thin: 1px;
  --border-thick: 1px;
  --shadow-1: 0 6px 18px rgba(68, 74, 80, 0.08);
  --shadow-2: 0 18px 44px rgba(68, 74, 80, 0.14);
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;
  --container: 1140px;
  --measure: 72ch;
  --gutter: 16px;
  --section-y: 88px;
  --section-y-lg: 123px;
}

/* ============================================================
   1. Reset 与中文排版基础
   ============================================================ */
*,
*::before,
*::after { box-sizing: border-box; }

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

body {
  margin: 0;
  background: 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;
}

img,
svg,
video { display: block; max-width: 100%; }

button,
input,
select,
textarea { font: inherit; color: inherit; }

ul,
ol { margin: 0; padding: 0; }

h1,
h2,
h3,
h4,
h5,
h6 {
  margin: 0 0 var(--space-3);
  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 { font-size: var(--text-lg); }

p { margin: 0 0 var(--space-3); }

a { color: var(--color-primary); text-decoration-thickness: 1px; text-underline-offset: 3px; }

.num,
[data-num] {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.02em;
}

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

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

.section {
  position: relative;
  padding-block: var(--section-y);
}

.section--lg { padding-block: var(--section-y-lg); }
.section--alt { background: var(--color-surface-alt); }
.section--deep { background: var(--color-surface-deep); }

.section--contrast {
  background: 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: var(--color-contrast-ink); }

.section + .section { border-top: var(--border-thin) dashed var(--color-line); }
.section--contrast + .section,
.section + .section--contrast { border-top-color: var(--color-contrast-line); }

.section-head { max-width: var(--measure); margin-bottom: var(--space-6); }

.section-title { margin-bottom: var(--space-2); }

.section-lead {
  font-size: var(--text-lg);
  color: var(--color-ink-soft);
  margin: 0;
}

.section--contrast .section-lead { color: var(--color-contrast-ink); }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
  text-transform: none;
}

.eyebrow::before {
  content: "";
  width: 22px;
  height: 1px;
  background: currentColor;
  opacity: 0.6;
}

.section--contrast .eyebrow { color: var(--color-contrast-accent); }

.grid {
  display: grid;
  gap: var(--space-4);
}

@media (min-width: 768px) {
  .grid--split { grid-template-columns: 7fr 5fr; }
  .grid--halves { grid-template-columns: 1fr 1fr; }
  .grid--thirds { grid-template-columns: repeat(3, 1fr); }
}

/* ============================================================
   3. 卡纸型容器
   ============================================================ */
.card {
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  box-shadow: var(--shadow-1);
}

.panel {
  background: var(--color-surface-alt);
  border: var(--border-thin) dashed var(--color-line);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
}

.section--alt .panel { background: var(--color-surface); }

.scoreboard {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  box-shadow: var(--shadow-2);
}

.scoreboard .num,
.scoreboard [data-num] { color: var(--color-contrast-accent); }

.scoreboard .divider { border-top-color: var(--color-contrast-line); }

/* ============================================================
   4. 标签与按钮
   ============================================================ */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 14px;
  border-radius: var(--radius-pill);
  background: var(--color-primary-soft);
  color: var(--color-ink);
  border: var(--border-thin) solid var(--color-line);
  font-size: var(--text-xs);
  line-height: 1.6;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.tag--accent {
  background: var(--color-highlight);
  border-color: color-mix(in srgb, var(--color-accent) 24%, transparent);
  color: var(--color-ink);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: 12px 24px;
  border-radius: var(--radius-pill);
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-surface);
  color: var(--color-ink);
  font-size: var(--text-sm);
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.18s ease, color 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
}

.btn:hover { background: var(--color-primary-soft); }
.btn:active { transform: translateY(1px); }

.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-contrast-surface)); }

.btn--accent {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: var(--color-accent-ink);
}

.btn--accent:hover { background: var(--color-focus); }

.btn--ghost {
  background: transparent;
  border-color: var(--color-line);
}

/* ============================================================
   5. 图文容器（画面贴在纸面上的效果）
   ============================================================ */
.media-frame {
  position: relative;
  padding: 10px;
  background: var(--color-surface-alt);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-1);
}

.media-frame__img {
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: calc(var(--radius-md) - 8px);
  object-fit: cover;
  background: linear-gradient(148deg, var(--color-surface-deep) 0%, var(--color-surface-alt) 56%, var(--color-highlight) 100%);
}

.media-frame--tall .media-frame__img { aspect-ratio: 4 / 5; }
.media-frame--wide .media-frame__img { aspect-ratio: 21 / 9; }

.media-frame--overlay::after {
  content: "";
  position: absolute;
  inset: 10px;
  border-radius: calc(var(--radius-md) - 8px);
  background: var(--overlay-scrim);
  pointer-events: none;
}

.media-frame__text {
  position: absolute;
  left: var(--space-4);
  right: var(--space-4);
  bottom: var(--space-4);
  z-index: 1;
  color: var(--color-contrast-ink);
}

.media-frame__text .eyebrow { color: var(--color-contrast-accent); }

.media-frame__caption {
  margin-top: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

/* ============================================================
   6. 数字组与进度
   ============================================================ */
.figure-cluster {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4) var(--space-6);
}

.figure { display: grid; gap: 4px; }
.figure:nth-child(even) { padding-top: var(--space-3); }

.figure__value {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: var(--text-figure);
  font-weight: var(--weight-heading);
  line-height: 1;
  letter-spacing: -0.01em;
  color: var(--color-primary);
}

.figure__label {
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

.scoreboard .figure__value { color: var(--color-contrast-accent); }
.scoreboard .figure__label { color: var(--color-contrast-ink); }

.meter {
  height: 8px;
  border-radius: var(--radius-pill);
  background: var(--color-surface-deep);
  overflow: hidden;
}

.meter__bar {
  height: 100%;
  width: 0;
  border-radius: inherit;
  background: var(--color-accent);
  transition: width 0.2s ease;
}

.scoreboard .meter { background: var(--color-contrast-line); }
.scoreboard .meter__bar { background: var(--color-contrast-accent); }

/* ============================================================
   7. 分隔、正文、面包屑
   ============================================================ */
.divider {
  border: 0;
  border-top: var(--border-thin) dashed var(--color-line);
  margin: var(--space-6) 0;
}

.divider--dots { border-top-style: dotted; }

.prose {
  max-width: var(--measure);
  font-size: var(--text-base);
  color: var(--color-ink);
}

.prose h2 { margin-top: var(--space-6); }
.prose h3 { margin-top: var(--space-4); color: var(--color-ink); }
.prose ul,
.prose ol { margin: 0 0 var(--space-3); padding-left: 1.3em; }
.prose li { margin-bottom: var(--space-1); }
.prose strong { font-weight: var(--weight-heading); }
.prose blockquote {
  margin: var(--space-4) 0;
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface-alt);
  border-left: 3px solid var(--color-accent);
  border-radius: var(--radius-md);
  color: var(--color-ink-soft);
}

.section--contrast .prose { color: var(--color-contrast-ink); }

.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  margin-bottom: var(--space-4);
  list-style: none;
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.breadcrumb li { display: inline-flex; align-items: center; gap: var(--space-1); }
.breadcrumb li + li::before { content: "/"; color: var(--color-line); }
.breadcrumb a { color: var(--color-ink-soft); text-decoration: none; }
.breadcrumb a:hover { color: var(--color-accent); text-decoration: underline; text-decoration-style: dotted; }

/* ============================================================
   8. 显现动效
   ============================================================ */
.reveal {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease, transform 0.5s ease;
  will-change: opacity, transform;
}

.reveal.is-in {
  opacity: 1;
  transform: none;
}

/* ============================================================
   9. 顶部导航（左右分置）
   ============================================================ */
.skip-link {
  position: absolute;
  left: var(--space-2);
  top: -120px;
  z-index: 200;
  padding: 10px 20px;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-size: var(--text-sm);
  text-decoration: none;
  transition: top 0.2s ease;
}

.skip-link:focus { top: var(--space-2); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 80;
  padding-block: var(--space-2);
  background: color-mix(in srgb, var(--color-surface) 90%, transparent);
  border-bottom: var(--border-thin) dashed var(--color-line);
  backdrop-filter: blur(10px);
}

.header-inner {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: 10px 16px 10px 18px;
  background: var(--color-surface);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-1);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--color-ink);
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  border-radius: var(--radius-sm);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-accent);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
}

.brand-text { display: grid; gap: 1px; }

.brand-name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.1;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.brand-sub {
  font-size: var(--text-xs);
  line-height: 1.4;
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
  list-style: none;
}

.nav-link {
  display: inline-block;
  padding: 8px 13px;
  border-radius: var(--radius-pill);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  text-decoration: none;
  transition: background 0.18s ease, color 0.18s ease;
}

.nav-link:hover {
  background: var(--color-primary-soft);
  color: var(--color-ink);
}

.nav-link[aria-current="page"] {
  color: var(--color-accent);
  background: var(--color-highlight);
  text-decoration: underline;
  text-decoration-style: dotted;
  text-decoration-thickness: 2px;
  text-underline-offset: 6px;
}

.nav-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 18px;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-size: var(--text-sm);
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.18s ease;
}

.nav-cta::before {
  content: "";
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--color-contrast-accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-contrast-accent) 34%, transparent);
}

.nav-cta:hover { background: var(--color-focus); }

.nav-toggle {
  display: none;
  align-items: center;
  gap: 8px;
  padding: 8px 15px;
  border-radius: var(--radius-pill);
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-primary-soft);
  color: var(--color-ink);
  cursor: pointer;
}

.nav-toggle-lines { display: grid; gap: 3px; }

.nav-toggle-bar {
  display: block;
  width: 15px;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
}

.nav-toggle-label {
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
}

.nav-toggle[aria-expanded="true"] {
  background: var(--color-highlight);
  border-color: color-mix(in srgb, var(--color-accent) 30%, transparent);
}

.header-progress {
  position: absolute;
  left: 20px;
  right: 20px;
  bottom: 6px;
  height: 2px;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
  transform: scaleX(0);
  transform-origin: left center;
  pointer-events: none;
}

@media (max-width: 1024px) {
  .nav-toggle { display: inline-flex; }

  .nav {
    display: none;
    position: absolute;
    left: 0;
    right: 0;
    top: calc(100% + 12px);
    flex-direction: column;
    align-items: stretch;
    gap: var(--space-2);
    padding: var(--space-3);
    background: var(--color-surface);
    border: var(--border-thin) solid var(--color-line);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-2);
  }

  .nav[data-open] { display: flex; }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
  }

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

  .nav-cta { justify-content: center; padding: 14px 18px; }

  .header-progress { left: 16px; right: 16px; }
}

/* ============================================================
   10. 阶梯式页脚
   ============================================================ */
.site-footer {
  margin-top: var(--section-y);
  background: var(--color-surface-alt);
  border-top: var(--border-thin) dashed var(--color-line);
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.footer-inner { padding-block: var(--space-8) var(--space-6); }

.footer-tier {
  display: grid;
  gap: var(--space-6);
}

@media (min-width: 768px) {
  .footer-tier { grid-template-columns: 1.5fr 1fr 1fr; }
}

.footer-brand-name {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-2xl);
  line-height: var(--leading-heading);
}

.footer-brand-note {
  max-width: 38ch;
  margin: 0 0 var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.footer-contact {
  display: grid;
  gap: 6px;
  list-style: none;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.footer-contact-key {
  display: inline-block;
  min-width: 5.4em;
  margin-right: var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  color: var(--color-ink-muted);
}

.footer-col-title {
  margin: 0 0 var(--space-2);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.16em;
  color: var(--color-ink-muted);
}

.footer-list {
  display: grid;
  gap: 2px;
  list-style: none;
}

.footer-list a {
  display: inline-block;
  padding: 6px 0;
  font-size: var(--text-sm);
  color: var(--color-ink);
  text-decoration: none;
  border-bottom: var(--border-thin) dotted transparent;
}

.footer-list a:hover {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2) var(--space-4);
  margin-top: var(--space-6);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-lg);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-xs);
}

.footer-legal-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  list-style: none;
}

.footer-legal-list a {
  color: var(--color-contrast-ink);
  text-decoration: none;
  border-bottom: var(--border-thin) dotted var(--color-contrast-line);
}

.footer-legal-list a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

.footer-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3);
  margin: 0;
}

.footer-icp { font-family: var(--font-mono); letter-spacing: 0.02em; }
.footer-lang { font-family: var(--font-mono); color: var(--color-contrast-accent); }
.footer-copy { color: var(--color-contrast-ink); }

/* ============================================================
   11. 无障碍与降级
   ============================================================ */
@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;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}

@media (max-width: 480px) {
  .header-inner { padding: 10px 12px; }
  .brand-sub { display: none; }
  .footer-legal { justify-content: flex-start; }
}