* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Georgia, 'Times New Roman', Times, serif;
  color: #333;
  background: #fff;
  line-height: 1.8;
  padding-bottom: 4rem;
}

.container {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.header {
  padding: 3.5rem 0 1.5rem;
  text-align: center;
  border-bottom: 1px solid #eee;
}

.header h1 {
  font-size: 2rem;
  font-weight: 400;
  letter-spacing: -0.5px;
  color: #111;
  margin-bottom: 0.3rem;
}

.last-updated {
  color: #999;
  font-size: 0.85rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.toc {
  padding: 1.5rem 0;
  margin: 1.5rem 0;
  border-bottom: 1px solid #eee;
}

.toc h2 {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: #999;
  margin-bottom: 0.8rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.toc ul {
  list-style: none;
  columns: 2;
  column-gap: 2rem;
}

.toc li {
  margin-bottom: 0.3rem;
}

.toc a {
  color: #555;
  text-decoration: none;
  font-size: 0.85rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  transition: color 0.2s;
}

.toc a:hover {
  color: #000;
}

section {
  padding: 1.5rem 0;
  border-bottom: 1px solid #f0f0f0;
}

section:last-of-type {
  border-bottom: none;
}

section h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.8rem;
  color: #111;
}

section h3 {
  font-size: 1rem;
  font-weight: 600;
  margin: 1.2rem 0 0.5rem;
  color: #222;
}

section p {
  margin-bottom: 0.8rem;
  color: #444;
}

section ul {
  margin: 0.5rem 0 1rem 1.5rem;
  color: #444;
}

section li {
  margin-bottom: 0.3rem;
}

section a {
  color: #333;
  text-decoration: underline;
  text-underline-offset: 2px;
}

section a:hover {
  color: #000;
}

.footer {
  text-align: center;
  padding: 2rem 0 0;
  color: #aaa;
  font-size: 0.85rem;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

.scroll-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid #ddd;
  background: #fff;
  color: #666;
  font-size: 1.1rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s, visibility 0.3s;
}

.scroll-top.visible {
  opacity: 1;
  visibility: visible;
}

.scroll-top:hover {
  border-color: #999;
  color: #333;
}

@media (max-width: 600px) {
  .header h1 {
    font-size: 1.5rem;
  }

  .toc ul {
    columns: 1;
  }

  section {
    padding: 1.2rem 0;
  }

  .scroll-top {
    bottom: 1rem;
    right: 1rem;
  }
}