:root {
  --color-surface: #f9f9f9;
  --color-surface-alt: #efefef;
  --color-surface-deep: #e1e1e1;
  --color-ink: #2d3134;
  --color-ink-soft: #595f63;
  --color-ink-muted: #757b80;
  --color-line: #d4d5d6;
  --color-primary: #0678cb;
  --color-primary-ink: #ffffff;
  --color-primary-soft: #d7e7f3;
  --color-accent: #518401;
  --color-accent-ink: #ffffff;
  --color-highlight: #dbe4cc;
  --color-focus: #4b7a00;
  --color-contrast-surface: #152530;
  --color-contrast-ink: #e4e6e7;
  --color-contrast-line: #434f58;
  --color-contrast-accent: #9cfe01;
  --overlay-scrim: linear-gradient(180deg, rgba(21, 37, 48, 0.35) 0%, rgba(21, 37, 48, 0.72) 55%, rgba(21, 37, 48, 0.92) 100%);
  --font-heading: "Source Han Sans SC", "Noto Sans SC", SimHei, "Microsoft YaHei", sans-serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", 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(52px, 10.8vw, 138px);
  --text-figure: clamp(44px, 7.7vw, 99px);
  --weight-heading: 897;
  --weight-body: 400;
  --leading-body: 1.77;
  --leading-heading: 1.16;
  --tracking-heading: -0.004em;
  --radius-sm: 112px;
  --radius-md: 338px;
  --radius-lg: 565px;
  --radius-pill: 999px;
  --border-thin: 2px;
  --border-thick: 2px;
  --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: 1100px;
  --measure: 72ch;
  --gutter: 24px;
  --section-y: 75px;
  --section-y-lg: 105px;
}

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

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

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);
}

img { display: block; max-width: 100%; height: auto; }

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

dl, dd, dt, figure, blockquote { margin: 0; }

button { font: inherit; color: inherit; }

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

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

/* ============ Typography ============ */
h1, h2, h3, h4, h5 {
  margin: 0;
  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); }
h5 { font-size: var(--text-base); }

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

strong, b { font-weight: var(--weight-heading); }

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

.skip-link {
  position: absolute;
  top: calc(var(--space-4) * -1);
  left: var(--space-2);
  z-index: 300;
  display: inline-block;
  padding: var(--space-2) var(--space-3);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  border-radius: var(--radius-pill);
  transition: top 0.18s ease;
}

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

/* ============ Layout utilities ============ */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

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

.section-head {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: var(--space-3);
  padding-bottom: var(--space-2);
  margin-bottom: var(--space-6);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.grid { display: grid; gap: var(--gutter); }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.prose { max-width: var(--measure); }
.prose > * + * { margin-top: var(--space-3); }

.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);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  color: var(--color-primary);
}

.data-label {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
  font-variant-numeric: tabular-nums;
}

/* ============ Dividers ============ */
.dotline {
  height: 0;
  margin: 0;
  border: 0;
  border-top: var(--border-thin) dashed var(--color-line);
}

.dotline-invert { border-top-color: var(--color-contrast-line); }

/* ============ Dark partition ============ */
.on-dark {
  background-color: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.on-dark h1,
.on-dark h2,
.on-dark h3,
.on-dark h4,
.on-dark h5 { color: var(--color-contrast-ink); }

.on-dark p,
.on-dark li,
.on-dark dd { color: var(--color-contrast-ink); }

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

.on-dark .eyebrow,
.on-dark .data-label { color: var(--color-contrast-accent); }

.on-dark .lede { color: color-mix(in srgb, var(--color-contrast-ink) 78%, transparent); }

.on-dark .dotline { border-top-color: var(--color-contrast-line); }

/* ============ Geometry pieces ============ */
.circle-numeral {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 auto;
  width: var(--space-6);
  height: var(--space-6);
  border-radius: var(--radius-pill);
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  font-variant-numeric: tabular-nums;
  transition: background-color 0.18s ease, color 0.18s ease;
}

.circle-numeral.is-accent {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}

.circle-numeral.is-outline {
  background: transparent;
  border: var(--border-thin) solid var(--color-primary);
  color: var(--color-primary);
}

.quote-indent {
  position: relative;
  max-width: var(--measure);
  margin-block: var(--space-6);
  padding-left: var(--space-6);
  border-left: var(--border-thick) solid var(--color-accent);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: 1.6;
  color: var(--color-ink);
}

.quote-indent::before {
  content: "\201C";
  position: absolute;
  left: var(--space-2);
  top: -0.12em;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-4xl);
  line-height: 1;
  color: var(--color-accent);
}

.on-dark .quote-indent {
  border-left-color: var(--color-contrast-accent);
  color: var(--color-contrast-ink);
}

.on-dark .quote-indent::before { color: var(--color-contrast-accent); }

/* ============ Buttons ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding: var(--space-2) var(--space-3);
  border: var(--border-thin) solid transparent;
  border-radius: var(--radius-pill);
  background: var(--color-primary);
  color: var(--color-primary-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  line-height: 1;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
}

.btn:hover { text-decoration: none; transform: translateY(-2px); }
.btn:active { transform: none; }

.btn-primary { background: var(--color-primary); color: var(--color-primary-ink); }
.btn-primary:hover { background: color-mix(in srgb, var(--color-primary) 82%, var(--color-ink)); }

.btn-accent { background: var(--color-accent); color: var(--color-accent-ink); }
.btn-accent:hover { background: color-mix(in srgb, var(--color-accent) 82%, var(--color-ink)); }

.btn-outline {
  background: transparent;
  border-color: var(--color-line);
  color: var(--color-ink);
}
.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: var(--color-primary-soft);
}

.btn-sm { padding: var(--space-1) var(--space-2); font-size: var(--text-xs); }

/* ============ Header ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--color-surface);
  border-bottom: var(--border-thin) solid var(--color-line);
  transition: background-color 0.2s ease;
}

.masthead { padding-block: var(--space-2); }

.masthead-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--space-3);
  min-height: var(--space-8);
}

.masthead-meta {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-ink-muted);
}

.tag-round {
  display: inline-flex;
  align-items: center;
  padding: calc(var(--space-1) / 2) var(--space-2);
  border: var(--border-thin) solid var(--color-primary);
  border-radius: var(--radius-pill);
  color: var(--color-primary);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  line-height: 1.4;
}

.masthead-place { font-family: var(--font-body); letter-spacing: 0.02em; }

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

.brand:hover { text-decoration: none; }

.brand-mark {
  width: var(--space-3);
  height: var(--space-3);
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: linear-gradient(90deg, var(--color-primary) 0 50%, var(--color-accent) 50% 100%);
}

.brand-name {
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  letter-spacing: var(--tracking-heading);
  line-height: 1;
}

.masthead-tools {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
  justify-self: end;
}

.tool-link {
  padding-block: var(--space-1);
  color: var(--color-ink-soft);
  font-size: var(--text-sm);
  text-decoration: none;
  border-bottom: var(--border-thin) dashed var(--color-line);
}

.tool-link:hover {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  text-decoration: none;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-2);
  background: transparent;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-pill);
  color: var(--color-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  line-height: 1;
  cursor: pointer;
}

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

.nav-toggle-bars {
  position: relative;
  display: block;
  width: var(--space-2);
  height: var(--space-1);
}

.nav-toggle-bars::before,
.nav-toggle-bars::after {
  content: "";
  position: absolute;
  left: 0;
  width: 100%;
  height: var(--border-thin);
  background: currentColor;
}

.nav-toggle-bars::before { top: 0; }
.nav-toggle-bars::after { bottom: 0; }

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

.nav-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  padding-block: var(--space-1);
}

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) var(--space-3);
  color: var(--color-ink-soft);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
  line-height: 1;
  text-decoration: none;
}

.nav-link::before {
  content: "";
  width: var(--space-1);
  height: var(--space-1);
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  border: var(--border-thin) solid var(--color-line);
  background: transparent;
  transition: background-color 0.18s ease, border-color 0.18s ease;
}

.nav-link:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.nav-link:hover::before { border-color: var(--color-primary); }

.nav-link[aria-current="page"] { color: var(--color-ink); }

.nav-link[aria-current="page"]::before {
  background: var(--color-primary);
  border-color: var(--color-primary);
}

.scroll-progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: var(--border-thin);
  background: var(--color-surface-deep);
  pointer-events: none;
}

.scroll-progress::after {
  content: "";
  display: block;
  height: 100%;
  width: var(--progress, 0%);
  background: var(--color-accent);
  transition: width 0.1s linear;
}

.site-header[data-condensed] .masthead { padding-block: var(--space-1); }
.site-header[data-condensed] .masthead-grid { min-height: var(--space-6); }
.site-header[data-condensed] .masthead-meta { display: none; }
.site-header[data-condensed] .brand-name { font-size: var(--text-base); }
.site-header[data-condensed] .nav-link { padding-block: var(--space-1); }

/* ============ Breadcrumbs ============ */
.breadcrumbs {
  padding-block: var(--space-3);
  border-bottom: var(--border-thin) dashed var(--color-line);
}

.breadcrumbs ol {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

.breadcrumbs li + li::before {
  content: "/";
  margin-right: var(--space-1);
  color: var(--color-line);
}

.breadcrumbs a { color: var(--color-ink-soft); }
.breadcrumbs a:hover { color: var(--color-primary); }

/* ============ Image containers ============ */
.figure {
  position: relative;
  margin: 0;
  overflow: hidden;
  background: var(--color-surface-deep);
}

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

.figure--wide { aspect-ratio: 16 / 9; }
.figure--tall { aspect-ratio: 3 / 4; }
.figure--square { aspect-ratio: 1 / 1; }
.figure--banner { aspect-ratio: 21 / 9; }

.figure-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--gutter);
}

.figure-grid .figure--span-2 { grid-column: span 2; }

.figure-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  gap: var(--space-2);
  padding: var(--space-4);
  background: var(--overlay-scrim);
  color: var(--color-contrast-ink);
}

.figure-overlay h3,
.figure-overlay h4,
.figure-overlay p,
.figure-overlay .data-label { color: var(--color-contrast-ink); }

.figure-caption {
  padding-top: var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--color-ink-muted);
}

/* ============ Reveal ============ */
.js [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.4s ease, transform 0.4s ease;
}

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

/* ============ Footer ============ */
.site-footer {
  margin-top: var(--section-y-lg);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.footer-inner { padding-block: var(--section-y) var(--space-4); }

.footer-lede {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: var(--space-6);
  padding-bottom: var(--space-4);
}

.footer-identity { max-width: 46ch; }

.footer-brand {
  display: inline-block;
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  text-decoration: none;
}

.footer-brand:hover { color: var(--color-contrast-accent); text-decoration: none; }

.footer-statement {
  margin: var(--space-2) 0 0;
  font-size: var(--text-sm);
  line-height: 1.7;
  color: color-mix(in srgb, var(--color-contrast-ink) 72%, transparent);
}

.footer-arc {
  position: relative;
  flex: 0 0 auto;
  width: var(--radius-sm);
  height: calc(var(--radius-sm) / 2);
  border: var(--border-thin) solid var(--color-contrast-line);
  border-bottom: 0;
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
}

.footer-arc::before,
.footer-arc::after {
  content: "";
  position: absolute;
  border-radius: var(--radius-pill);
  background: var(--color-contrast-accent);
}

.footer-arc::before {
  width: var(--space-1);
  height: var(--space-1);
  left: 20%;
  top: 42%;
}

.footer-arc::after {
  width: calc(var(--space-1) / 2);
  height: calc(var(--space-1) / 2);
  right: 24%;
  top: 20%;
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  padding-block: var(--space-4);
  border-top: var(--border-thin) dashed var(--color-contrast-line);
  border-bottom: var(--border-thin) dashed var(--color-contrast-line);
}

.footer-nav a {
  color: var(--color-contrast-ink);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-sm);
  text-decoration: none;
  border-bottom: var(--border-thin) dashed transparent;
  transition: color 0.18s ease, border-color 0.18s ease;
}

.footer-nav a:hover {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
  text-decoration: none;
}

.footer-contact {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: var(--space-3);
  padding-block: var(--space-4);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
}

.footer-contact dt {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-contrast-accent);
}

.footer-contact dd {
  margin-top: var(--space-1);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: var(--color-contrast-ink);
}

.footer-base {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
  padding-top: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: color-mix(in srgb, var(--color-contrast-ink) 66%, transparent);
}

.footer-base p { margin: 0; }

.footer-base a {
  color: color-mix(in srgb, var(--color-contrast-ink) 80%, transparent);
  text-decoration: none;
}

.footer-base a:hover { color: var(--color-contrast-accent); text-decoration: none; }

/* ============ Responsive ============ */
@media (max-width: 900px) {
  .grid-2,
  .grid-3 { grid-template-columns: minmax(0, 1fr); }

  .figure-grid .figure--span-2 { grid-column: span 1; }
}

@media (max-width: 860px) {
  .masthead-grid { grid-template-columns: auto 1fr; }
  .masthead-meta { display: none; }
  .brand { justify-self: start; }
  .masthead-tools { justify-self: end; }
  .nav-toggle { display: inline-flex; }

  .site-nav {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.26s ease;
  }

  .site-nav[data-open] {
    max-height: 70vh;
    overflow-y: auto;
  }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding-block: var(--space-2);
  }

  .nav-link {
    justify-content: flex-start;
    padding: var(--space-2) 0;
    font-size: var(--text-base);
    border-bottom: var(--border-thin) dashed var(--color-line);
  }

  .nav-link:last-child,
  .nav-list li:last-child .nav-link { border-bottom: 0; }

  .footer-lede { align-items: flex-start; }
  .footer-arc { width: var(--space-8); height: var(--space-4); }
}

@media (max-width: 520px) {
  .tool-link { display: none; }
  .footer-base { flex-direction: column; align-items: flex-start; }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }

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