:root {
  color-scheme: light;
  --bg-start: #ffffff;
  --bg-end: #f3f4f6;
  --card: #ffffff;
  --ink: #0f172a;
  --muted: #475569;
  --border: #e2e8f0;
  --accent: #0ea5e9;
  --accent-ink: #0c4a6e;
  --accent-bg: #f0f9ff;
  --shadow: 0 18px 40px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  color: var(--ink);
  background: linear-gradient(180deg, var(--bg-start), var(--bg-end));
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.page {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.site-header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding: 18px 24px;
  border-bottom: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand {
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  font-size: 0.78rem;
  color: var(--ink);
}

.nav a {
  margin-left: 16px;
  font-size: 0.95rem;
  color: var(--muted);
}

main {
  flex: 1;
  padding: 48px 20px 80px;
}

.doc {
  max-width: 880px;
  margin: 0 auto;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 40px;
  box-shadow: var(--shadow);
}

.doc h1 {
  font-size: 2.4rem;
  margin: 0 0 12px;
}

.doc .meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
  color: var(--muted);
  font-size: 0.95rem;
  margin-bottom: 18px;
}

.doc .subtle {
  color: var(--muted);
  margin-top: 0;
}

.doc h2 {
  font-size: 1.2rem;
  margin-top: 28px;
}

.doc p {
  line-height: 1.7;
  margin: 12px 0;
}

.doc ul {
  padding-left: 20px;
  margin: 12px 0;
}

.doc li {
  margin: 8px 0;
  line-height: 1.6;
}

.doc .callout {
  border-left: 4px solid var(--accent);
  padding: 12px 16px;
  background: var(--accent-bg);
  color: var(--accent-ink);
  border-radius: 12px;
  margin: 16px 0;
}

.footer {
  text-align: center;
  padding: 24px;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 640px) {
  .site-header {
    padding: 14px 18px;
  }

  main {
    padding: 32px 16px 60px;
  }

  .doc {
    padding: 28px 22px;
    border-radius: 18px;
  }

  .doc h1 {
    font-size: 2rem;
  }
}