:root {
  --bg: #f9fafb;
  --text: #111827;
  --muted: #4b5563;
  --link: #2563eb;
  --card: #ffffff;
  --border: #e5e7eb;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, BlinkMacSystemFont,
               "Segoe UI", Roboto, Ubuntu, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.7;
}

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

a:hover {
  text-decoration: underline;
}

.container {
  max-width: 820px;
  margin: 0 auto;
  padding: 80px 20px;
}

header {
  margin-bottom: 48px;
}

nav {
  margin-top: 12px;
}

nav a {
  margin-right: 14px;
  font-weight: 500;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 28px;
  margin-bottom: 28px;
}

h1 {
  font-size: 42px;
  margin: 0 0 12px;
}

h2 {
  font-size: 26px;
  margin-top: 0;
}

p {
  font-size: 18px;
  color: var(--muted);
}

ul {
  padding-left: 20px;
}

footer {
  margin-top: 60px;
  font-size: 14px;
  color: #6b7280;
}