body {
  margin: 0;
  font-family: Arial, sans-serif;
  display: flex;
  height: 100vh;
}

.page-header {
  text-align: center;
}

.sidebar {
  width: 250px;
  background-color: #111;
  color: white;
  padding-top: 20px;
  overflow-y: auto;
  text-decoration: none;
}

.sidebar h2 {
  text-align: center;
  margin-bottom: 20px;
  font-size: 1.4em;
}

.nav-item {
  padding: 10px 20px;
  cursor: pointer;
  background-color: #111;
  border: none;
  text-align: left;
  width: 100%;
  color: white;
  outline: none;
  text-decoration: none;
  font-size: 16px;
  font-family: Arial, sans-serif;
}

.nav-item:hover {
  background-color: #333;
}

.sub-menu {
  display: none;
  padding-left: 20px;
  background-color: #222;
  font-size: 16px;
  font-family: Arial, sans-serif;
}

.sub-menu .sub-item {
  padding: 8px 20px;
  cursor: pointer;
  color: #ccc;
  display: block;
  text-decoration: none;
  font-size: 16px;
  font-family: Arial, sans-serif;
}

.sub-menu .sub-item:hover {
  background-color: #444;
  color: white;
}

.content {
  flex: 1;
  padding: 20px;
}

.active {
  display: block !important;
}