:root {
  color-scheme: light;
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #17202a;
  --muted: #5d6978;
  --line: #dfe4ea;
  --accent: #0f766e;
  --accent-dark: #115e59;
  --ink: #111827;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
}

a {
  color: inherit;
  text-decoration: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 16px clamp(20px, 5vw, 72px);
  background: rgba(246, 247, 249, 0.92);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(14px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
}

.brand-mark {
  display: inline-grid;
  width: 36px;
  height: 36px;
  place-items: center;
  border-radius: 8px;
  background: var(--ink);
  color: #ffffff;
  font-size: 13px;
  letter-spacing: 0;
}

.top-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  color: var(--muted);
  font-size: 14px;
}

.top-nav a {
  padding: 8px 10px;
  border-radius: 6px;
}

.top-nav a:hover {
  background: #e8edf2;
  color: var(--text);
}

main {
  width: min(1180px, calc(100% - 40px));
  margin: 0 auto;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(280px, 0.85fr);
  gap: 28px;
  min-height: 520px;
  align-items: center;
  padding: 56px 0 42px;
}

.hero-copy h1,
.article h1 {
  margin: 8px 0 18px;
  color: var(--ink);
  font-size: clamp(40px, 6vw, 76px);
  line-height: 1.05;
  letter-spacing: 0;
}

.lead {
  max-width: 760px;
  margin: 0;
  color: var(--muted);
  font-size: 18px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--accent-dark);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}

.primary-action,
.secondary-action,
.download-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 18px;
  border-radius: 7px;
  font-weight: 700;
}

.primary-action {
  background: var(--accent);
  color: #ffffff;
}

.secondary-action,
.download-link {
  border: 1px solid var(--line);
  background: #ffffff;
  color: var(--text);
}

.hero-panel,
.feature-card,
.content-section,
.method-block,
.principles > div {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.hero-panel {
  padding: 24px;
}

.hero-panel dl,
.hero-panel dd {
  margin: 0;
}

.hero-panel div + div {
  margin-top: 18px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.hero-panel dt {
  color: var(--muted);
  font-size: 13px;
}

.hero-panel dd {
  margin-top: 6px;
  color: var(--ink);
  font-weight: 700;
}

.section-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}

.feature-card {
  min-height: 210px;
  padding: 24px;
}

.feature-card:hover {
  border-color: var(--accent);
}

.card-index {
  color: var(--accent-dark);
  font-weight: 800;
}

.feature-card h2,
.section-heading h2,
.article h2 {
  margin: 10px 0 10px;
  color: var(--ink);
  letter-spacing: 0;
}

.feature-card p,
.timeline p,
.article p,
.principles p {
  margin: 0;
  color: var(--muted);
}

.content-section {
  margin: 24px 0;
  padding: 28px;
}

.section-heading {
  margin-bottom: 20px;
}

.timeline {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 14px;
}

.timeline article {
  padding: 14px;
  border-left: 3px solid var(--accent);
  background: #f8fafc;
}

.timeline span {
  display: inline-grid;
  width: 28px;
  height: 28px;
  place-items: center;
  border-radius: 999px;
  background: var(--accent);
  color: #ffffff;
  font-size: 13px;
  font-weight: 800;
}

.timeline h3 {
  margin: 12px 0 6px;
  color: var(--ink);
  font-size: 16px;
}

.video-shell video {
  display: block;
  width: 100%;
  max-height: 620px;
  border-radius: 8px;
  background: #111827;
}

.download-link {
  margin-top: 14px;
}

.page-links {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.page-links a {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: #f8fafc;
  color: var(--ink);
  font-weight: 700;
}

.site-footer {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding: 28px clamp(20px, 5vw, 72px);
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 14px;
}

.article-layout {
  width: min(960px, calc(100% - 40px));
}

.article {
  padding: 46px 0 80px;
}

.article h1 {
  font-size: clamp(38px, 5vw, 64px);
}

.article h2 {
  margin-top: 38px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.method-block {
  margin: 14px 0;
  padding: 18px;
}

.method-block h3,
.principles h3 {
  margin: 0 0 8px;
  color: var(--ink);
}

.principles {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.principles > div {
  padding: 18px;
}

.flow-diagram {
  display: grid;
  grid-template-columns: repeat(11, auto);
  align-items: center;
  gap: 10px;
  overflow-x: auto;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
}

.flow-diagram div {
  min-width: 112px;
  padding: 14px;
  border-radius: 7px;
  background: #ecfdf5;
  color: #064e3b;
  text-align: center;
  font-weight: 800;
}

.flow-diagram span {
  width: 34px;
  height: 2px;
  background: var(--accent);
}

.tree {
  overflow-x: auto;
  padding: 18px;
  border-radius: 8px;
  background: #101827;
  color: #e5e7eb;
  line-height: 1.7;
}

blockquote {
  margin: 28px 0 0;
  padding: 18px 20px;
  border-left: 4px solid var(--accent);
  background: #ffffff;
  color: var(--ink);
  font-weight: 700;
}

@media (max-width: 860px) {
  .site-header,
  .site-footer {
    align-items: flex-start;
    flex-direction: column;
  }

  .hero,
  .section-grid,
  .timeline,
  .principles,
  .page-links {
    grid-template-columns: 1fr;
  }

  .hero {
    min-height: auto;
    padding-top: 34px;
  }

  .hero-copy h1,
  .article h1 {
    font-size: 42px;
  }
}