:root {
  --bg-color: #ffffff;
  --text-color: #333333;
  --sidebar-bg: #f3f3f3;
  --sidebar-width: 240px;
}
[data-theme="dark"] {
  --bg-color: #222222;
  --text-color: #eeeeee;
  --sidebar-bg: #333333;
}
body {
  margin: 0;
  background: var(--bg-color);
  color: var(--text-color);
  font-family: Arial, sans-serif;
}
.header {
  display: flex;
  align-items: center;
  padding: 0.5rem 1rem;
  background: var(--sidebar-bg);
}
.logo { text-decoration: none; color: var(--text-color); font-weight: bold; }
.sidebar-toggle,
.theme-toggle { background: none; border: none; font-size: 1.2rem; margin-right: 1rem; cursor: pointer; }
.container { display: flex; }
.sidebar {
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  padding: 1rem;
}
.sidebar ul { list-style: none; padding: 0; }
.sidebar a { text-decoration: none; color: var(--text-color); }
main {
  flex: 1;
  padding: 1rem;
}
.breadcrumbs a { color: var(--text-color); text-decoration: none; }
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    left: -100%;
    top: 0;
    height: 100%;
    overflow-y: auto;
    transition: left 0.3s ease;
    z-index: 1000;
  }
  body.sidebar-open .sidebar { left: 0; }
}