:root {
  --color-surface: #f9f9f9;
  --color-surface-alt: #f0f0f0;
  --color-surface-deep: #e5e3e5;
  --color-ink: #4f444f;
  --color-ink-soft: #776977;
  --color-ink-muted: #877886;
  --color-line: #dad8da;
  --color-primary: #956493;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #ebe4eb;
  --color-accent: #c82dbf;
  --color-accent-ink: #ffffff;
  --color-highlight: #f0d4ef;
  --color-focus: #c31eb9;
  --color-contrast-surface: #231d23;
  --color-contrast-ink: #e7e4e7;
  --color-contrast-line: #4e494e;
  --color-contrast-accent: #d74ccf;
  --overlay-scrim: linear-gradient(180deg, rgba(35, 29, 35, 0.35) 0%, rgba(35, 29, 35, 0.72) 55%, rgba(35, 29, 35, 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: 7.8px;
  --text-sm: 12.6px;
  --text-base: 16px;
  --text-lg: 25.9px;
  --text-xl: 41.9px;
  --text-2xl: 67.8px;
  --text-3xl: 109.7px;
  --text-4xl: 177.4px;
  --text-display: clamp(40px, 8.3vw, 106px);
  --text-figure: clamp(33px, 5.9vw, 76px);
  --weight-heading: 348;
  --weight-body: 400;
  --leading-body: 1.88;
  --leading-heading: 1.18;
  --tracking-heading: 0.035em;
  --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: 1140px;
  --measure: 61ch;
  --gutter: 16px;
  --section-y: 125px;
  --section-y-lg: 175px;
}

/* ---------- 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;
}
h1, h2, h3, h4, h5, h6, p, figure, blockquote, dl, dd, ul, ol { margin: 0; }
ul, ol { padding: 0; list-style: none; }
img, picture, svg, video { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button, input, select, textarea { font: inherit; color: inherit; }
button { padding: 0; border: 0; background: none; cursor: pointer; }
:focus-visible { outline: calc(var(--border-thick) * 2) solid var(--color-focus); outline-offset: 3px; }
::selection { background-color: var(--color-highlight); color: var(--color-ink); }
[id] { scroll-margin-top: calc(var(--space-8) + var(--space-2)); }

/* ---------- 中文排版 ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
}
p + p { margin-top: var(--space-2); }
.numeral, time, code, .detail-table .mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

.display-title {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 1.08;
  letter-spacing: var(--tracking-heading);
}
.section-title { font-size: var(--text-xl); }
.lede { font-size: var(--text-lg); line-height: 1.5; color: var(--color-ink-soft); max-width: var(--measure); }
.eyebrow {
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-primary);
  font-family: var(--font-body);
}
.caption {
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-soft);
  line-height: 1.7;
}
.numeral { font-size: var(--text-lg); color: var(--color-accent); line-height: 1; }
.figure-value { font-family: var(--font-mono); font-size: var(--text-figure); line-height: 1.05; color: var(--color-accent); }
.mark { background-image: linear-gradient(transparent 62%, var(--color-highlight) 62%); background-repeat: no-repeat; }
.mark--line { border-bottom: calc(var(--border-thick) * 2) solid var(--color-primary); }
.prose { max-width: var(--measure); }
.stack { display: grid; gap: var(--space-2); }

/* ---------- 布局 ---------- */
.container, .container-fluid { width: 100%; margin-inline: auto; padding-inline: var(--space-4); }
.container { max-width: var(--container); }
.container-fluid { max-width: calc(var(--container) + var(--space-8) * 2); }
.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-9 { grid-column: span 9; }
.col-12 { grid-column: span 12; }

.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 .caption, .section--contrast .eyebrow { color: var(--color-contrast-accent); }
.section--contrast .numeral, .section--contrast .figure-value { color: var(--color-contrast-accent); }
.pull-left { margin-inline: calc(var(--space-6) * -1) 0; }

/* ---------- 图片与视觉块 ---------- */
.figure-frame {
  position: relative;
  overflow: hidden;
  background-color: var(--color-surface-deep);
  aspect-ratio: 3 / 2;
}
.figure-frame > img { width: 100%; height: 100%; object-fit: cover; }
.figure-frame--square { aspect-ratio: 1 / 1; }
.figure-frame--portrait { aspect-ratio: 3 / 4; }
.figure-frame--wide { aspect-ratio: 16 / 9; }
.figure-scrim { position: absolute; inset: 0; background-image: var(--overlay-scrim); pointer-events: none; }
.figure-label {
  position: absolute;
  inset-inline-start: var(--space-3);
  bottom: var(--space-3);
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
}
.figure-caption { margin-top: var(--space-2); margin-inline-start: var(--space-4); max-width: 46ch; }

/* ---------- 明细表 ---------- */
.detail-table { width: 100%; border-collapse: collapse; }
.detail-table caption {
  text-align: start;
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-soft);
  padding-bottom: var(--space-2);
}
.detail-table th, .detail-table td {
  padding: var(--space-2) var(--space-2) var(--space-2) 0;
  text-align: start;
  vertical-align: top;
  border-bottom: var(--border-thin) solid var(--color-line);
}
.detail-table thead th {
  font-family: var(--font-body);
  font-weight: var(--weight-body);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}
.detail-table tbody tr[data-active] { background-color: var(--color-primary-soft); }
.section--contrast .detail-table th,
.section--contrast .detail-table td { border-bottom-color: var(--color-contrast-line); }

/* ---------- 步骤路径 ---------- */
.step-track { display: grid; gap: var(--space-6); }
.step-item {
  display: grid;
  grid-template-columns: minmax(48px, auto) minmax(0, 1fr);
  gap: var(--space-3);
  padding-bottom: var(--space-4);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.step-index { font-family: var(--font-mono); font-size: var(--text-lg); line-height: 1; color: var(--color-accent); }
.step-body { display: grid; gap: var(--space-1); }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) var(--space-4);
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink);
  transition: background-color 180ms ease, color 180ms ease, border-color 180ms ease;
}
.btn--primary { background-color: var(--color-primary); border-color: var(--color-primary); color: var(--color-primary-ink); }
.btn--primary:hover { background-color: var(--color-focus); border-color: var(--color-focus); }
.btn--ghost:hover { background-color: var(--color-primary-soft); border-color: var(--color-primary); }

/* ---------- 面包屑 ---------- */
.breadcrumb { font-size: var(--text-sm); letter-spacing: 0.08em; color: var(--color-ink-muted); }
.breadcrumb-list { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-1); }
.breadcrumb-item + .breadcrumb-item::before { content: "／"; margin-inline-end: var(--space-1); color: var(--color-ink-muted); }

/* ---------- 章节目录 ---------- */
.toc { position: sticky; top: calc(var(--space-8) * 1.6); font-size: var(--text-sm); letter-spacing: 0.08em; }
.toc-list { display: grid; gap: var(--space-1); }
.toc-link {
  display: block;
  padding: var(--space-1) var(--space-2);
  border-inline-start: var(--border-thin) solid var(--color-line);
  color: var(--color-ink-muted);
  transition: color 180ms ease, background-color 180ms ease;
}
.toc-link[data-current] { color: var(--color-primary); background-color: var(--color-primary-soft); border-inline-start-color: var(--color-primary); }

/* ---------- 返回顶部 ---------- */
.to-top {
  position: fixed;
  right: var(--space-4);
  bottom: var(--space-4);
  z-index: 70;
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  opacity: 0;
  visibility: hidden;
  transition: opacity 240ms cubic-bezier(0.22, 0.61, 0.36, 1), visibility 240ms linear;
}
.to-top[data-visible] { opacity: 1; visibility: visible; }

/* ---------- 显现 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 240ms cubic-bezier(0.22, 0.61, 0.36, 1), transform 240ms cubic-bezier(0.22, 0.61, 0.36, 1);
}
.reveal[data-revealed] { opacity: 1; transform: none; }

/* ---------- skip link ---------- */
.skip-link {
  position: absolute;
  inset-inline-start: var(--space-2);
  top: var(--space-2);
  z-index: 90;
  padding: var(--space-1) var(--space-3);
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  transform: translateY(-200%);
}
.skip-link:focus { transform: translateY(0); }

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background-color: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
}
.header-inner {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding-block: var(--space-2);
  transition: padding 240ms cubic-bezier(0.22, 0.61, 0.36, 1);
}
.site-header[data-condensed] .header-inner { padding-block: var(--space-1); }
.site-header[data-condensed] .header-batch { display: none; }

.brand { display: inline-flex; align-items: center; gap: var(--space-2); margin-inline-end: auto; }
.brand-mark {
  display: grid;
  place-items: center;
  width: 32px;
  height: 32px;
  background-color: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-heading);
  font-size: var(--text-base);
  line-height: 1;
}
.brand-text { display: grid; gap: 2px; }
.brand-name { font-family: var(--font-heading); font-weight: var(--weight-heading); font-size: var(--text-base); letter-spacing: var(--tracking-heading); }
.brand-line { font-size: var(--text-sm); letter-spacing: 0.08em; color: var(--color-ink-muted); }

.nav-toggle {
  display: none;
  align-items: center;
  padding: var(--space-1) var(--space-2);
  border: var(--border-thin) solid var(--color-line);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink);
}
.nav-toggle-close { display: none; }
.site-header[data-open] .nav-toggle-open { display: none; }
.site-header[data-open] .nav-toggle-close { display: inline; }

.site-nav { display: block; }
.nav-list { display: flex; align-items: center; gap: var(--space-3); }
.nav-link {
  display: inline-block;
  padding-block: var(--space-1);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink);
  border-bottom: calc(var(--border-thick) * 2) solid transparent;
  transition: color 180ms ease, border-color 180ms ease;
}
.nav-link:hover { color: var(--color-primary); }
.nav-link[aria-current="page"] { color: var(--color-primary); border-bottom-color: var(--color-primary); }

.header-batch {
  display: flex;
  align-items: baseline;
  gap: var(--space-1);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
  white-space: nowrap;
}
.header-batch-value { font-family: var(--font-mono); color: var(--color-accent); }
.header-batch-note { color: var(--color-ink-muted); }

.header-progress { position: relative; height: 1px; background-color: var(--color-line); }
.header-progress-bar {
  position: absolute;
  inset-inline-start: 0;
  top: 0;
  height: 100%;
  width: 100%;
  background-color: var(--color-accent);
  transform: scaleX(0);
  transform-origin: left center;
}

/* ---------- footer ---------- */
.site-footer { background-color: var(--color-surface); }
.footer-band { background-color: var(--color-contrast-surface); color: var(--color-contrast-ink); }
.footer-band-inner {
  display: grid;
  grid-template-columns: minmax(0, auto) minmax(0, 1fr) minmax(0, auto);
  align-items: baseline;
  gap: var(--space-3);
  padding-block: var(--space-4);
}
.footer-band-label { font-size: var(--text-sm); letter-spacing: 0.08em; color: var(--color-contrast-accent); }
.footer-band-text { font-size: var(--text-sm); line-height: 1.9; color: var(--color-contrast-ink); max-width: var(--measure); }
.footer-band-meta { font-family: var(--font-mono); font-size: var(--text-sm); color: var(--color-contrast-ink); white-space: nowrap; }

.footer-line {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  gap: var(--space-3);
  padding-block: var(--space-3);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}
.footer-brand { font-family: var(--font-heading); color: var(--color-ink); white-space: nowrap; }
.footer-links { display: flex; align-items: center; gap: var(--space-2); margin-inline-end: auto; }
.footer-link { color: var(--color-ink-soft); border-bottom: var(--border-thin) solid transparent; transition: color 180ms ease, border-color 180ms ease; }
.footer-link:hover { color: var(--color-primary); border-bottom-color: var(--color-primary); }
.footer-legal, .footer-contact, .footer-year { font-family: var(--font-mono); white-space: nowrap; }

/* ---------- 响应式 ---------- */
@media (max-width: 1080px) {
  .header-batch-note { display: none; }
  .footer-band-inner { grid-template-columns: minmax(0, 1fr); gap: var(--space-2); }
  .footer-band-meta { white-space: normal; }
}

@media (max-width: 900px) {
  :root { --section-y: 80px; --section-y-lg: 104px; }
  .nav-toggle { display: inline-flex; }
  .site-nav {
    position: absolute;
    inset-inline: 0;
    top: 100%;
    display: none;
    background-color: var(--color-surface);
    border-bottom: var(--border-thin) solid var(--color-line);
    padding: var(--space-2) var(--space-4) var(--space-3);
  }
  .site-nav[data-open] { display: block; }
  .nav-list { flex-direction: column; align-items: stretch; gap: 0; }
  .nav-item + .nav-item { border-top: var(--border-thin) solid var(--color-line); }
  .nav-link { display: block; padding-block: var(--space-2); border-bottom: 0; }
  .nav-link[aria-current="page"] { color: var(--color-primary); }
  .header-batch { display: none; }
  .pull-left { margin-inline: 0; }
  .footer-line { flex-wrap: wrap; gap: var(--space-2); }
  .footer-links { margin-inline-end: 0; }
  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9 { grid-column: span 12; }
  .toc { position: static; }
}

@media (max-width: 600px) {
  .container, .container-fluid { padding-inline: var(--space-3); }
  .figure-caption { margin-inline-start: 0; }
  .footer-line { font-size: var(--text-sm); }
  .to-top { right: var(--space-2); bottom: var(--space-2); }
}

/* ---------- 动效退化 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    transition-duration: 1ms !important;
    animation-duration: 1ms !important;
    animation-iteration-count: 1 !important;
  }
  .reveal { opacity: 1; transform: none; }
}