#side-nav {
  position: fixed;
  top: 30%;
  left: 1rem;
  background: rgba(255, 255, 255, 0.9);
  padding: 0.5rem;
  border-radius: 0.5rem;
  z-index: 999;
  transition: opacity 0.3s ease;
}
#side-nav.hidden {
  opacity: 0;
  pointer-events: none;
}
#side-nav ul {
  list-style: none;
  padding: 0;
}
#side-nav li {
  margin-bottom: 0.5rem;
}
#side-nav a {
  text-decoration: none;
  color: #333;
  font-weight: bold;
}