:root {
  --fg: #1a1a1a;
  --muted: #666;
  --bg: #fafaf7;
  --card: #ffffff;
  --accent: #2c5aa0;
  --border: #e5e5e0;
  --max: 760px;
}

* { box-sizing: border-box; }

html { font-size: 17px; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.65;
  color: var(--fg);
  background: var(--bg);
}

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

header {
  background: var(--card);
  border-bottom: 1px solid var(--border);
}

nav {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1rem 1.2rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 1rem;
}

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--fg);
  margin-right: auto;
}

nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  gap: 1.2rem;
  flex-wrap: wrap;
}

nav ul a { color: var(--muted); font-size: 0.95rem; }
nav ul a:hover { color: var(--accent); }

main {
  max-width: var(--max);
  margin: 2.5rem auto 4rem;
  padding: 0 1.2rem;
}

h1 {
  font-size: 1.9rem;
  margin: 0 0 0.5rem;
  letter-spacing: -0.01em;
}

h2 {
  font-size: 1.3rem;
  margin: 2.2rem 0 0.6rem;
  letter-spacing: -0.005em;
}

h3 {
  font-size: 1.05rem;
  margin: 1.6rem 0 0.4rem;
}

p { margin: 0.8rem 0; }

.lede {
  color: var(--muted);
  font-size: 1.05rem;
  margin-bottom: 2rem;
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
  margin: 2rem 0;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.2rem;
}

.card h3 { margin-top: 0; }

.card p {
  color: var(--muted);
  font-size: 0.95rem;
  margin-bottom: 0.5rem;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 2rem;
  font-size: 0.95rem;
}

th, td {
  text-align: left;
  padding: 0.55rem 0.7rem;
  border-bottom: 1px solid var(--border);
  vertical-align: top;
}

th {
  background: var(--card);
  font-weight: 600;
  color: var(--muted);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

code {
  background: #f0efea;
  padding: 0.1em 0.35em;
  border-radius: 3px;
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 0.9em;
}

blockquote {
  border-left: 3px solid var(--accent);
  margin: 1rem 0;
  padding: 0.3rem 0 0.3rem 1rem;
  color: var(--muted);
  font-style: italic;
}

ul.notes li { margin: 0.4rem 0; }

footer {
  border-top: 1px solid var(--border);
  margin-top: 4rem;
  padding: 1.5rem 1.2rem;
  text-align: center;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 540px) {
  html { font-size: 16px; }
  nav { padding: 0.8rem 1rem; }
  .logo { font-size: 1rem; flex-basis: 100%; margin-right: 0; }
  main { margin-top: 1.5rem; }
}