.dropdown-menu {
        display: none;
        opacity: 0;
         transition: opacity 0.3s ease-in-out; 
    }
    .dropdown:hover .dropdown-menu {
        display: block;
        opacity: 1;
    }
 
    /* Add animation for the dropdown */
    /* Multi-layer dropdown */
    .dropdown-submenu {
        position: relative;
    }
    .dropdown-submenu .submenu {
        display: none;
        position: absolute;
        top: 0;
        left: 100%;
        margin-top: -1px;
    }
    .dropdown-submenu:hover .submenu {
        display: block;
    }