:root {
  --ink: #1e293b;
  --muted: #64748b;
  --line: #cbd5e1;
  --soft: #f1f5f9;
  --paper: #e8eef5;
  --brand: #0f766e;
  --brand-deep: #115e59;
  --accent: #14b8a6;
  --spine: #94a3b8;
  --tile: #ffffff;
  --max: 1040px;
  --radius: 12px;
  --shadow: 0 8px 24px rgba(15, 23, 42, 0.08);
  font-family: "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--ink);
  background:
    linear-gradient(180deg, #f8fafc 0%, var(--paper) 45%, #e2e8f0 100%);
  line-height: 1.78;
  min-height: 100vh;
}

a { color: var(--brand-deep); text-underline-offset: 3px; }
a:hover { color: var(--accent); }
img { max-width: 100%; height: auto; display: block; }
.wrap { width: min(100% - 2rem, var(--max)); margin-inline: auto; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(248, 250, 252, 0.94);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(8px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.65rem 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--ink);
  text-decoration: none;
  font-weight: 700;
}
.brand img { width: 36px; height: 36px; border-radius: 8px; object-fit: cover; }

.nav-desktop { display: flex; gap: 1rem; flex-wrap: wrap; }
.nav-desktop a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.92rem;
}
.nav-desktop a:hover { color: var(--brand); }

.menu-toggle {
  display: none;
  border: 1px solid var(--line);
  background: var(--tile);
  color: var(--ink);
  border-radius: 8px;
  padding: 0.4rem 0.75rem;
  cursor: pointer;
  font-size: 0.9rem;
}

#mobile-nav {
  display: none;
  flex-direction: column;
  gap: 0.35rem;
  padding: 0.5rem 1rem 1rem;
  border-top: 1px solid var(--line);
  background: var(--soft);
}
#mobile-nav.open { display: flex; }
#mobile-nav a {
  color: var(--ink);
  text-decoration: none;
  padding: 0.45rem 0.2rem;
}

.tl-intro {
  padding: 1.75rem 0 0.5rem;
  text-align: center;
}
.tl-intro h1 {
  margin: 0 0 0.75rem;
  font-size: clamp(1.35rem, 3.2vw, 1.85rem);
  line-height: 1.35;
  color: var(--ink);
}
.tl-intro .lead {
  margin: 0 auto;
  max-width: 42rem;
  color: var(--muted);
  font-size: 1.02rem;
}
.tl-badge {
  display: inline-block;
  margin-bottom: 0.75rem;
  padding: 0.2rem 0.65rem;
  border-radius: 999px;
  background: rgba(20, 184, 166, 0.12);
  color: var(--brand-deep);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
}

.tl-spine {
  position: relative;
  padding: 2rem 0 3rem;
}
.tl-spine::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 3px;
  margin-left: -1.5px;
  background: linear-gradient(180deg, transparent, var(--spine) 8%, var(--accent) 50%, var(--spine) 92%, transparent);
  border-radius: 2px;
}

.tl-item {
  position: relative;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.5rem;
  align-items: center;
  margin-bottom: 2.75rem;
}
.tl-item::after {
  content: "";
  position: absolute;
  left: 50%;
  top: 50%;
  width: 14px;
  height: 14px;
  margin: -7px 0 0 -7px;
  border-radius: 50%;
  background: var(--accent);
  border: 3px solid var(--tile);
  box-shadow: 0 0 0 2px var(--brand);
  z-index: 2;
}

.tl-item.flip .tl-media { order: 2; }
.tl-item.flip .tl-body { order: 1; text-align: right; }
.tl-item:not(.flip) .tl-body { padding-left: 0.5rem; }
.tl-item.flip .tl-body { padding-right: 0.5rem; }

.tl-media figure {
  margin: 0;
  background: var(--tile);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.tl-media img { width: 100%; aspect-ratio: 16/10; object-fit: cover; }
.tl-media figcaption {
  padding: 0.55rem 0.85rem;
  font-size: 0.85rem;
  color: var(--muted);
  background: var(--soft);
}

.tl-body h2 {
  margin: 0 0 0.55rem;
  font-size: 1.2rem;
  color: var(--brand-deep);
}
.tl-body p { margin: 0 0 0.7rem; color: var(--ink); }
.tl-step {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.06em;
  margin-bottom: 0.35rem;
}

.tl-prose {
  background: var(--tile);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem 1.35rem;
  margin: 0 0 2rem;
  box-shadow: var(--shadow);
}
.tl-prose h2 { margin: 1.4rem 0 0.6rem; font-size: 1.15rem; color: var(--brand-deep); }
.tl-prose h2:first-child { margin-top: 0; }
.tl-prose h3 { margin: 1.1rem 0 0.45rem; font-size: 1.05rem; }
.tl-prose p { margin: 0 0 0.85rem; }
.tl-prose ul { margin: 0 0 1rem; padding-left: 1.2rem; }
.tl-prose li { margin-bottom: 0.35rem; }

.peer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem 1rem;
  align-items: center;
  margin: 1.25rem 0;
  padding: 0.85rem 1rem;
  background: var(--soft);
  border-radius: 10px;
  border: 1px dashed var(--line);
}
.peer-links a {
  color: var(--brand);
  font-weight: 600;
  text-decoration: none;
}
.peer-links a:hover { text-decoration: underline; }

.faq details {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.65rem 0.9rem;
  margin-bottom: 0.55rem;
  background: var(--soft);
}
.faq summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--ink);
}
.faq details p { margin: 0.5rem 0 0.15rem; color: var(--muted); }

.site-footer {
  border-top: 1px solid var(--line);
  background: #0f172a;
  color: #cbd5e1;
  padding: 1.4rem 0;
  margin-top: 1rem;
}
.site-footer a { color: #99f6e4; text-decoration: none; }
.site-footer a:hover { text-decoration: underline; }
.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.1rem;
  margin-bottom: 0.65rem;
}
.site-footer p { margin: 0; font-size: 0.9rem; color: #94a3b8; }

.page-hero { padding: 1.75rem 0 0.5rem; }
.page-hero h1 { margin: 0 0 0.4rem; font-size: 1.55rem; }
.muted { color: var(--muted); }
.prose { padding-bottom: 2rem; }
.prose h2 { margin: 1.35rem 0 0.5rem; font-size: 1.15rem; color: var(--brand-deep); }
.prose p { margin: 0 0 0.85rem; }

.err-box {
  text-align: center;
  padding: 3.5rem 0 4rem;
}
.err-box h1 { margin: 0 0 0.75rem; }
.btn {
  display: inline-block;
  padding: 0.55rem 1.1rem;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 600;
}
.btn-primary {
  background: var(--brand);
  color: #fff;
}
.btn-primary:hover { background: var(--brand-deep); color: #fff; }

@media (max-width: 860px) {
  .nav-desktop { display: none; }
  .menu-toggle { display: inline-block; }
  .tl-spine::before {
    left: 12px;
    margin-left: 0;
  }
  .tl-item {
    grid-template-columns: 1fr;
    gap: 0.85rem;
    padding-left: 2rem;
  }
  .tl-item::after {
    left: 12px;
    top: 1.2rem;
    margin-left: -7px;
  }
  .tl-item.flip .tl-media,
  .tl-item.flip .tl-body { order: unset; }
  .tl-item.flip .tl-body,
  .tl-item:not(.flip) .tl-body {
    text-align: left;
    padding: 0;
  }
}

/* SEO keyword highlight */
strong.kw, .kw{color:var(--accent,var(--brand,#c43b2c));font-weight:700}
mark.kw{background:rgba(196,59,44,.12);color:inherit;padding:0 .15em;border-radius:3px}