:root {
  --bg: #f3f6f8;
  --surface: #ffffff;
  --ink: #142033;
  --muted: #5b6b7c;
  --line: #d7e0e8;
  --accent: #0f766e;
  --accent-soft: #d9f3ef;
  --hero-from: #0b1c2c;
  --hero-to: #16324a;
  --max: 46rem;
  --nav: 14rem;
  --font-display: "Newsreader", "Source Serif 4", Georgia, serif;
  --font-body: "Public Sans", "Segoe UI", sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;
}

html[lang="zh"] {
  --font-display: "Noto Serif SC", "Newsreader", Georgia, serif;
  --font-body: "Noto Sans SC", "Public Sans", "Segoe UI", sans-serif;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 10% -10%, #d7ece8 0%, transparent 55%),
    radial-gradient(900px 420px at 90% 0%, #d9e5f2 0%, transparent 50%),
    var(--bg);
  font-family: var(--font-body);
  font-size: 1.05rem;
  line-height: 1.7;
}

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

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

a:hover {
  color: #0b5f59;
}

.hero {
  position: relative;
  background: linear-gradient(145deg, var(--hero-from), var(--hero-to));
  color: #edf3f8;
  padding: 4.5rem 1.25rem 3.5rem;
}

.hero-bar {
  width: min(100% - 2rem, calc(var(--max) + var(--nav) + 3rem));
  margin: -2.6rem auto 1.6rem;
  display: flex;
  justify-content: flex-end;
}

.lang-switch {
  display: inline-flex;
  gap: 0.2rem;
  padding: 0.18rem;
  border: 1px solid rgba(255, 255, 255, 0.28);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.06);
}

.lang-switch button {
  font: inherit;
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  cursor: pointer;
  border: 0;
  border-radius: 999px;
  padding: 0.28rem 0.7rem;
  background: transparent;
  color: #c5d5e4;
}

.lang-switch button:hover {
  color: #fff;
}

.lang-switch button.active {
  background: #14b8a6;
  color: #042f2e;
  font-weight: 600;
}

.hero-inner,
.page {
  width: min(100% - 2rem, calc(var(--max) + var(--nav) + 3rem));
  margin: 0 auto;
}

.hero-inner {
  max-width: var(--max);
}

.kicker {
  margin: 0 0 0.75rem;
  font-size: 0.82rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: #9fb6c9;
}

.hero h1 {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(2.4rem, 5vw, 3.4rem);
  font-weight: 600;
  line-height: 1.12;
  letter-spacing: -0.02em;
}

.tagline {
  margin: 1rem 0 0;
  max-width: 38rem;
  font-size: 1.15rem;
  color: #c5d5e4;
}

.links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin-top: 1.6rem;
}

.links a {
  display: inline-flex;
  align-items: center;
  padding: 0.55rem 0.95rem;
  border: 1px solid rgba(255, 255, 255, 0.28);
  border-radius: 999px;
  color: #f4f8fb;
  text-decoration: none;
  background: rgba(255, 255, 255, 0.06);
  font-size: 0.95rem;
}

.links a:hover {
  background: rgba(255, 255, 255, 0.14);
  color: #fff;
}

.links a.primary {
  background: #14b8a6;
  border-color: #14b8a6;
  color: #042f2e;
  font-weight: 600;
}

.links a.disabled {
  opacity: 0.45;
  pointer-events: none;
  cursor: default;
}

.layout {
  display: grid;
  grid-template-columns: var(--nav) minmax(0, var(--max));
  gap: 2.5rem;
  width: min(100% - 2rem, calc(var(--max) + var(--nav) + 3rem));
  margin: 0 auto;
  padding: 2.5rem 0 4rem;
}

.toc {
  position: sticky;
  top: 1.25rem;
  align-self: start;
  padding: 0.2rem 0;
}

.toc p {
  margin: 0 0 0.7rem;
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
}

.toc a {
  display: block;
  padding: 0.28rem 0;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.92rem;
}

.toc a:hover,
.toc a.active {
  color: var(--accent);
}

main section {
  margin-bottom: 2.8rem;
  scroll-margin-top: 1.2rem;
}

.section-kicker {
  margin: 0 0 0.35rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  color: var(--accent);
}

html[lang="zh"] .section-kicker {
  letter-spacing: 0.18em;
}

main h2 {
  margin: 0 0 0.9rem;
  font-family: var(--font-display);
  font-size: 1.85rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

main h3 {
  margin: 1.4rem 0 0.55rem;
  font-size: 1.1rem;
}

.lead,
main p {
  margin: 0 0 1rem;
  color: #243447;
}

.lead {
  font-size: 1.12rem;
}

.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.8rem;
  margin: 1.3rem 0 1.6rem;
}

.stat {
  padding: 0.95rem 1rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 0.7rem;
}

.stat strong {
  display: block;
  font-family: var(--font-display);
  font-size: 1.55rem;
  line-height: 1.1;
  color: var(--accent);
}

.stat span {
  display: block;
  margin-top: 0.3rem;
  font-size: 0.86rem;
  color: var(--muted);
}

figure {
  margin: 1.2rem 0 0.4rem;
  padding: 0.85rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 0.85rem;
}

figure img,
figure video {
  width: 100%;
  border-radius: 0.35rem;
}

figure video {
  background: #0b1c2c;
}

figcaption {
  margin-top: 0.7rem;
  font-size: 0.9rem;
  color: var(--muted);
}

.loop {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin: 1rem 0 1.2rem;
}

.loop span {
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: #115e59;
  font-size: 0.88rem;
  font-weight: 600;
}

ul.clean {
  margin: 0.4rem 0 1rem;
  padding-left: 1.15rem;
}

ul.clean li {
  margin: 0.35rem 0;
}

.citation {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 0.85rem;
  overflow: hidden;
}

.citation-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.65rem 0.9rem;
  border-bottom: 1px solid var(--line);
  background: #eef3f7;
  font-size: 0.88rem;
  color: var(--muted);
}

.citation button {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  border-radius: 999px;
  padding: 0.3rem 0.75rem;
  cursor: pointer;
  font: inherit;
  font-size: 0.85rem;
}

.citation button:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.citation pre {
  margin: 0;
  padding: 1rem 1.05rem 1.15rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.84rem;
  line-height: 1.55;
  white-space: pre-wrap;
}

.note {
  margin-top: 1.2rem;
  padding: 0.85rem 1rem;
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  color: #134e4a;
  font-size: 0.95rem;
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 1.4rem 1.25rem 2.4rem;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}

.site-footer p {
  margin: 0.45rem 0;
}

.site-footer img {
  display: inline-block;
  margin: 0.2rem auto 0;
}

.site-footer .footer-meta {
  margin-top: 0.8rem;
  font-size: 0.84rem;
}

@media (max-width: 920px) {
  .layout {
    grid-template-columns: 1fr;
    gap: 1.2rem;
  }

  .toc {
    position: static;
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem 1rem;
    padding-bottom: 0.4rem;
    border-bottom: 1px solid var(--line);
  }

  .toc p {
    width: 100%;
  }

  .stats {
    grid-template-columns: 1fr;
  }

  .growth-grid {
    grid-template-columns: 1fr;
  }
}

.growth-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}

.growth-grid video {
  width: 100%;
  height: auto;
  display: block;
  background: #0b1c2c;
  border-radius: 0.35rem;
}

.growth-fallback {
  margin: 0.45rem 0 0;
  font-size: 0.86rem;
}