:root {
  --bg: #f7fbff;
  --card: #ffffff;
  --text: #0f172a;
  --muted: #475569;
  --border: #dbeafe;
  --link: #075985;
  --accent: #0284c7;
  --soft: #e0f2fe;
  --max: 920px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: linear-gradient(180deg, var(--bg), #ffffff 460px);
  color: var(--text);
  line-height: 1.6;
}
a { color: var(--link); }
a:hover { text-decoration-thickness: 2px; }
.site-header {
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,0.86);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav {
  max-width: var(--max);
  margin: 0 auto;
  padding: 14px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.brand {
  font-weight: 800;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.02em;
}
.nav-links {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  font-size: 0.95rem;
}
.nav-links a { text-decoration: none; color: var(--muted); }
.nav-links a:hover { color: var(--link); }
main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 48px 20px 72px;
}
.hero {
  padding: 42px 0 28px;
}
h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  line-height: 1.08;
  margin: 0 0 16px;
  letter-spacing: -0.055em;
}
h2 {
  margin-top: 2.2em;
  font-size: 1.45rem;
  letter-spacing: -0.025em;
  border-top: 1px solid var(--border);
  padding-top: 1.1em;
}
h3 { margin-top: 1.6em; font-size: 1.1rem; }
p, li { color: var(--text); }
.lede { font-size: 1.12rem; color: var(--muted); max-width: 720px; }
.meta { color: var(--muted); font-size: 0.95rem; }
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
  margin-top: 28px;
}
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 22px;
  box-shadow: 0 10px 30px rgba(14, 116, 144, 0.07);
}
.card h2, .card h3 { border-top: 0; padding-top: 0; margin-top: 0; }
.button-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 24px; }
.button {
  display: inline-block;
  padding: 10px 16px;
  border-radius: 999px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-weight: 700;
}
.button.secondary { background: #fff; color: var(--link); }
.notice {
  border: 1px solid var(--border);
  background: var(--soft);
  border-radius: 18px;
  padding: 18px 20px;
  margin: 24px 0;
}
code {
  background: #f1f5f9;
  border: 1px solid #e2e8f0;
  padding: 0.12em 0.32em;
  border-radius: 6px;
}
ul { padding-left: 1.4rem; }
footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 28px 20px 60px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.95rem;
}
@media (max-width: 620px) {
  .nav { align-items: flex-start; flex-direction: column; }
  main { padding-top: 28px; }
  .hero { padding-top: 24px; }
}