:root {
  --color-surface: #f8f8f8;
  --color-surface-alt: #efeff0;
  --color-surface-deep: #e3e3e4;
  --color-ink: #484752;
  --color-ink-soft: #6d6c79;
  --color-ink-muted: #7a7986;
  --color-line: #d8d8da;
  --color-primary: #75738c;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #e6e5e9;
  --color-accent: #2e1fe0;
  --color-accent-ink: #ffffff;
  --color-highlight: #d4d1f4;
  --color-focus: #2312ed;
  --color-contrast-surface: #1f1e22;
  --color-contrast-ink: #e4e4e7;
  --color-contrast-line: #4a4a4d;
  --color-contrast-accent: #8279ec;
  --overlay-scrim: linear-gradient(180deg, rgba(31, 30, 34, 0.35) 0%, rgba(31, 30, 34, 0.72) 55%, rgba(31, 30, 34, 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: 9.8px;
  --text-sm: 14.7px;
  --text-base: 18px;
  --text-lg: 27.0px;
  --text-xl: 40.5px;
  --text-2xl: 60.8px;
  --text-3xl: 91.1px;
  --text-4xl: 136.7px;
  --text-display: clamp(46px, 9.4vw, 120px);
  --text-figure: clamp(38px, 6.7vw, 86px);
  --weight-heading: 414;
  --weight-body: 400;
  --leading-body: 1.86;
  --leading-heading: 1.15;
  --tracking-heading: 0.009em;
  --radius-sm: 0px;
  --radius-md: 0px;
  --radius-lg: 0px;
  --radius-pill: 0px;
  --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: 67ch;
  --gutter: 32px;
  --section-y: 98px;
  --section-y-lg: 137px;
}

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

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

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;
}

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  text-wrap: balance;
}

p { margin: 0; text-wrap: pretty; }

ul, ol { margin: 0; padding: 0; list-style: none; }

figure, figcaption, blockquote, address { margin: 0; font-style: normal; }

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

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.18s ease;
}

a:hover {
  text-decoration: underline;
  text-underline-offset: 0.28em;
  text-decoration-thickness: var(--border-thin);
}

[hidden] { display: none !important; }

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

::selection {
  background-color: var(--color-highlight);
  color: var(--color-ink);
}

/* ============ 2. 中文排版与正文 ============ */
.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-6);
}

.prose ul,
.prose ol { padding-left: 1.4em; }

.prose li { margin-top: var(--space-1); }

.prose li::marker { color: var(--color-ink-muted); }

.prose strong { font-weight: 600; }

.mark {
  background-color: var(--color-highlight);
  padding: 0 0.12em;
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* ============ 3. 布局骨架 ============ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: 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; }
.offset-1 { grid-column-start: 2; }
.offset-2 { grid-column-start: 3; }

.section { padding-block: var(--section-y); }
.section--tight { padding-block: var(--space-8); }
.section--alt { background-color: var(--color-surface-alt); }
.section--contrast {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}
.section--contrast a { color: var(--color-contrast-accent); }

.section__head {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--space-3) var(--gutter);
  align-items: end;
  margin-bottom: var(--space-6);
}

.section__title {
  grid-column: span 8;
  font-size: var(--text-2xl);
  color: inherit;
}

.section__lead {
  grid-column: span 4;
  font-size: var(--text-sm);
  line-height: 1.9;
  color: var(--color-ink-soft);
}

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

.hero-title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  margin: 0;
}

.eyebrow {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.4em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

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

.chapter-no {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  line-height: 1;
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
  color: var(--color-primary);
}

.data-figure {
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  letter-spacing: -0.03em;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}

.stat {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.stat__value {
  font-family: var(--font-mono);
  font-size: var(--text-xl);
  line-height: 1.05;
  font-variant-numeric: tabular-nums;
  color: var(--color-ink);
}

.stat__label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.section--contrast .stat__value { color: var(--color-contrast-ink); }
.section--contrast .stat__label { color: var(--color-contrast-ink); opacity: 0.7; }

.rule {
  height: var(--border-thin);
  background-color: var(--color-line);
  border: 0;
  margin: 0;
}

.rule--offset {
  width: 62%;
  margin-left: auto;
}

.rule--contrast { background-color: var(--color-contrast-line); }

/* ============ 4. 通用按钮与链接元件 ============ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-body);
  font-size: var(--text-sm);
  letter-spacing: 0.2em;
  line-height: 1;
  padding: var(--space-2) 0;
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.18s ease, background-color 0.18s ease;
}

.btn:hover {
  text-decoration: underline;
  text-underline-offset: 0.4em;
}

.btn--solid {
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
}

.btn--solid:hover {
  background-color: var(--color-focus);
  color: var(--color-accent-ink);
  text-decoration: none;
}

.btn--ghost { color: var(--color-ink); }
.btn--ghost:hover { color: var(--color-accent); }

.btn--contrast { color: var(--color-contrast-accent); }
.btn--contrast:hover { color: var(--color-contrast-ink); }

.btn--contrast-solid {
  padding: var(--space-3) var(--space-4);
  background-color: var(--color-contrast-accent);
  color: var(--color-contrast-surface);
}

.btn--contrast-solid:hover {
  background-color: var(--color-contrast-ink);
  color: var(--color-contrast-surface);
  text-decoration: none;
}

.copy-btn {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.18em;
  color: var(--color-accent);
  padding: var(--space-1) 0 var(--space-1) var(--space-2);
  transition: color 0.18s ease;
}

.copy-btn:hover {
  text-decoration: underline;
  text-underline-offset: 0.3em;
}

.copy-btn[data-copied="true"] { color: var(--color-ink-muted); }

.breadcrumb {
  padding-block: var(--space-3);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0 var(--space-2);
}

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

.breadcrumb li + li::before {
  content: "／";
  color: var(--color-line);
}

.breadcrumb a { color: var(--color-ink-soft); }
.breadcrumb a:hover { color: var(--color-accent); }
.breadcrumb [aria-current="page"] { color: var(--color-ink); }

/* ============ 5. 面板、标签、筛选 ============ */
.panel {
  padding: var(--space-4);
  background-color: var(--color-surface-alt);
}

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

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

.panel--contrast a { color: var(--color-contrast-accent); }

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0 var(--space-3);
}

.tag {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.section--contrast .tag { color: var(--color-contrast-ink); opacity: 0.72; }

.filter-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2);
  padding-block: var(--space-2);
}

.filter-btn {
  font-family: var(--font-body);
  font-size: var(--text-sm);
  letter-spacing: 0.18em;
  padding: var(--space-1) var(--space-3);
  color: var(--color-ink-soft);
  transition: color 0.18s ease, background-color 0.18s ease;
}

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

.filter-btn[aria-pressed="true"] {
  background-color: var(--color-accent);
  color: var(--color-accent-ink);
}

.filter-btn[aria-pressed="true"]:hover { color: var(--color-accent-ink); }

.filter-status {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  color: var(--color-ink-muted);
}

/* ============ 6. 图片容器 ============ */
.img-frame {
  position: relative;
  display: block;
  overflow: hidden;
  background-color: var(--color-surface-deep);
}

.img-frame > img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.img-frame--wide { aspect-ratio: 16 / 9; }
.img-frame--tall { aspect-ratio: 3 / 4; }
.img-frame--square { aspect-ratio: 1 / 1; }
.img-frame--panorama { aspect-ratio: 21 / 9; }

.img-frame--scrim::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--overlay-scrim);
  pointer-events: none;
}

.img-frame__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
  padding: var(--space-3);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  line-height: 1.7;
  letter-spacing: 0.06em;
}

.img-frame__caption a { color: var(--color-contrast-accent); }

.img-figure { display: block; }

.img-figure figcaption {
  margin-top: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
}

/* ============ 7. 头部 ============ */
.skip-link {
  position: absolute;
  left: var(--space-2);
  top: -72px;
  z-index: 200;
  padding: var(--space-2) var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.12em;
  transition: top 0.18s ease;
}

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

.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  background-color: var(--color-surface);
  background-color: color-mix(in srgb, var(--color-surface) 92%, transparent);
  -webkit-backdrop-filter: saturate(120%) blur(8px);
  backdrop-filter: saturate(120%) blur(8px);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.header-inner { position: relative; }

.masthead {
  padding-block: var(--space-4) var(--space-2);
  text-align: center;
}

.masthead__brand {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-1);
  color: var(--color-ink);
  text-decoration: none;
}

.masthead__brand:hover {
  color: var(--color-ink);
  text-decoration: none;
}

.masthead__mark {
  display: block;
  width: 28px;
  height: 3px;
  background-color: var(--color-primary);
}

.masthead__title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  letter-spacing: 0.16em;
  text-indent: 0.16em;
  color: inherit;
}

.masthead__sub {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.34em;
  text-indent: 0.34em;
  color: var(--color-ink-muted);
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2);
  font-size: var(--text-sm);
  letter-spacing: 0.2em;
  color: var(--color-ink);
  transition: color 0.18s ease;
}

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

.nav-toggle__bars {
  display: inline-flex;
  flex-direction: column;
  justify-content: space-between;
  width: 20px;
  height: 9px;
}

.nav-toggle__bars span {
  display: block;
  height: 1px;
  background-color: currentColor;
}

.site-nav {
  border-top: var(--border-thin) solid var(--color-line);
}

.site-nav__list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 0 var(--space-6);
}

.site-nav__link {
  display: inline-block;
  padding-block: var(--space-2);
  font-size: var(--text-sm);
  letter-spacing: 0.24em;
  text-indent: 0.24em;
  color: var(--color-ink);
  transition: color 0.18s ease;
}

.site-nav__link:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.site-nav__link[aria-current="page"] {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-thickness: var(--border-thin);
  text-underline-offset: 0.55em;
}

/* ============ 8. 页脚 ============ */
.site-footer {
  margin-top: var(--section-y);
  padding-block: var(--space-8) var(--space-6);
  background-color: var(--color-surface-alt);
}

.footer-cta {
  padding: var(--space-8) var(--space-6);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.footer-cta__eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.36em;
  text-transform: uppercase;
  color: var(--color-contrast-accent);
}

.footer-cta__title {
  margin-top: var(--space-3);
  max-width: 20em;
  font-size: var(--text-xl);
  color: var(--color-contrast-ink);
}

.footer-cta__text {
  margin-top: var(--space-3);
  max-width: var(--measure);
  font-size: var(--text-sm);
  line-height: 1.9;
  color: var(--color-contrast-ink);
  opacity: 0.82;
}

.footer-cta__actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3) var(--space-6);
  margin-top: var(--space-6);
}

.footer-cards {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
  margin-top: var(--space-6);
}

.footer-card {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  padding: var(--space-4);
  background-color: var(--color-surface);
}

.footer-card--brand { grid-column: span 5; }
.footer-card--nav { grid-column: span 3; margin-top: var(--space-4); }
.footer-card--contact { grid-column: span 4; margin-top: var(--space-8); }

.footer-card__title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 400;
  letter-spacing: 0.34em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.footer-card__body {
  font-size: var(--text-sm);
  line-height: 1.9;
  color: var(--color-ink-soft);
}

.footer-nav__list {
  display: flex;
  flex-direction: column;
}

.footer-nav__link {
  display: block;
  padding-block: var(--space-1);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink);
  transition: color 0.18s ease;
}

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

.footer-contact {
  display: grid;
  gap: var(--space-2);
}

.footer-contact__row {
  display: grid;
  grid-template-columns: 4.4em minmax(0, 1fr);
  gap: var(--space-2);
  align-items: baseline;
  font-size: var(--text-sm);
  line-height: 1.8;
}

.footer-contact__label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.24em;
  color: var(--color-ink-muted);
}

.footer-contact__value {
  color: var(--color-ink);
  overflow-wrap: anywhere;
}

.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-3);
  margin-top: var(--space-6);
  padding-top: var(--space-3);
  border-top: var(--border-thin) solid var(--color-line);
}

.footer-base__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
}

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

/* ============ 9. 动效与状态 ============ */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  z-index: 200;
  pointer-events: none;
}

.scroll-progress__bar {
  display: block;
  height: 100%;
  width: 100%;
  transform: scaleX(0);
  transform-origin: 0 50%;
  background-color: var(--color-accent);
}

[data-reveal] {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}

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

/* ============ 10. 响应式 ============ */
@media (max-width: 900px) {
  .grid,
  .section__head,
  .footer-cards {
    grid-template-columns: repeat(6, minmax(0, 1fr));
  }

  .col-3, .col-4, .col-5 { grid-column: span 3; }
  .col-6, .col-7, .col-8, .col-12 { grid-column: span 6; }
  .offset-1, .offset-2 { grid-column-start: auto; }

  .section__title,
  .section__lead { grid-column: span 6; }

  .section { padding-block: var(--space-8); }
  .section--tight { padding-block: var(--space-6); }

  .masthead {
    padding-block: var(--space-2) var(--space-1);
    text-align: left;
  }

  .masthead__brand { align-items: flex-start; }

  .masthead__title {
    font-size: var(--text-lg);
    letter-spacing: 0.1em;
    text-indent: 0;
  }

  .masthead__sub {
    letter-spacing: 0.22em;
    text-indent: 0;
  }

  .nav-toggle {
    display: inline-flex;
    position: absolute;
    top: var(--space-2);
    right: 0;
  }

  .site-nav { display: none; }

  .site-header[data-open] .site-nav { display: block; }

  .site-nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding-bottom: var(--space-2);
  }

  .site-nav__item + .site-nav__item {
    border-top: var(--border-thin) solid var(--color-line);
  }

  .site-nav__link {
    display: block;
    padding-block: var(--space-3);
    font-size: var(--text-base);
    letter-spacing: 0.18em;
    text-indent: 0;
  }

  .footer-cta { padding: var(--space-6) var(--space-4); }
  .footer-cta__title { font-size: var(--text-lg); }

  .footer-card--brand,
  .footer-card--nav,
  .footer-card--contact {
    grid-column: span 6;
    margin-top: 0;
  }

  .footer-card--nav,
  .footer-card--contact { margin-top: var(--space-3); }
}

@media (max-width: 600px) {
  .grid,
  .section__head,
  .footer-cards {
    grid-template-columns: 1fr;
  }

  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-12,
  .section__title,
  .section__lead,
  .footer-card--brand,
  .footer-card--nav,
  .footer-card--contact {
    grid-column: span 1;
  }

  .masthead__title { font-size: var(--text-lg); }

  .footer-contact__row {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .footer-base { flex-direction: column; align-items: flex-start; }

  .rule--offset { width: 100%; }
}

@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 !important;
    transform: none !important;
  }

  .scroll-progress { display: none; }
}