:root {
  --bg: #ffffff;
  --text: #0f1b5c;
  --text-muted: #5a6478;
  --border: #e2e8f0;
  --primary: #1976d2;
  --primary-dark: #0f1b5c;
  --max-width: 760px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

header {
  background: var(--primary-dark);
  color: white;
  padding: 24px 16px;
  border-bottom: 4px solid var(--primary);
}

header .container {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

header h1 {
  margin: 0;
  font-size: 22px;
  font-weight: 800;
  letter-spacing: -0.5px;
}

header .byline {
  color: #42a5f5;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  margin-top: 2px;
}

nav {
  display: flex;
  gap: 16px;
  font-size: 14px;
}

nav a {
  color: white;
  text-decoration: none;
  opacity: 0.85;
  transition: opacity 0.15s;
}

nav a:hover, nav a.active {
  opacity: 1;
  text-decoration: underline;
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 16px 64px;
}

main h1 {
  font-size: 32px;
  margin: 0 0 24px;
  letter-spacing: -0.5px;
}

main h2 {
  font-size: 22px;
  margin: 32px 0 12px;
  color: var(--primary-dark);
}

main h3 {
  font-size: 18px;
  margin: 24px 0 8px;
}

main h4 {
  font-size: 16px;
  margin: 16px 0 4px;
  color: var(--text-muted);
}

main p {
  margin: 0 0 12px;
}

main a {
  color: var(--primary);
}

main ul, main ol {
  padding-left: 24px;
  margin: 0 0 12px;
}

main li {
  margin: 4px 0;
}

main strong {
  color: var(--primary-dark);
  font-weight: 700;
}

main hr {
  border: 0;
  border-top: 1px solid var(--border);
  margin: 32px 0;
}

main code {
  background: #f1f5f9;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0 24px;
  font-size: 14px;
}

th, td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

th {
  background: #f8fafc;
  font-weight: 700;
  font-size: 13px;
}

footer {
  background: #f8fafc;
  border-top: 1px solid var(--border);
  padding: 24px 16px;
  font-size: 13px;
  color: var(--text-muted);
  text-align: center;
}

footer .container {
  max-width: var(--max-width);
  margin: 0 auto;
}

footer a { color: var(--primary); text-decoration: none; }
footer a:hover { text-decoration: underline; }

.lead {
  font-size: 18px;
  color: var(--text-muted);
  margin: 0 0 24px;
}

.callout {
  background: #fff4e6;
  border-left: 4px solid #f59e0b;
  padding: 12px 16px;
  margin: 16px 0;
  font-size: 14px;
  border-radius: 0 6px 6px 0;
}

@media (max-width: 600px) {
  main h1 { font-size: 24px; }
  main h2 { font-size: 18px; }
  header h1 { font-size: 18px; }
  nav { width: 100%; }
}