.sidebar-center {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: #f4f4f4;
    padding: 2rem 1.5rem;
    border-radius: 12px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
    z-index: 1000;
  }
  
  .submenu {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    align-items: center;
  }
  
  .submenu a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    transition: background 0.2s;
    white-space: nowrap;
  }
  
  .submenu a:hover {
    background-color: #e0e0e0;
  }