:root {
  --bg: #f9fafb;
  --sidebar: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --accent: #2563eb;
  --border: #e5e7eb;
}

* {
  box-sizing: border-box;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
  background: white;
  position: sticky;
  top: 0;
}

.logo {
  font-size: 20px;
  font-weight: 600;
}

.topbar input {
  padding: 8px 12px;
  width: 220px;
  border-radius: 6px;
  border: 1px solid var(--border);
}

.layout {
  display: flex;
  min-height: calc(100vh - 60px);
}

.sidebar {
  width: 240px;
  padding: 20px;
  background: var(--sidebar);
  border-right: 1px solid var(--border);
}

.sidebar h3 {
  margin-top: 0;
  font-size: 14px;
  color: var(--muted);
  text-transform: uppercase;
}

.sidebar ul {
  list-style: none;
  padding: 0;
}

.sidebar li {
  padding: 8px 0;
  cursor: pointer;
  color: var(--accent);
}

.sidebar li:hover {
  text-decoration: underline;
}

.content {
  padding: 30px;
  max-width: 900px;
}

.content section {
  margin-bottom: 40px;
}

.subtitle {
  color: var(--muted);
}

.footer {
  text-align: center;
  padding: 15px;
  font-size: 13px;
  color: var(--muted);
}

@media (max-width: 768px) {
  .layout {
    flex-direction: column;
  }
  .sidebar {
    width: 100%;
    border-right: none;
    border-bottom: 1px solid var(--border);
  }
}