* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
/* Menu chính */
.menu {
    display: flex;
    list-style: none;
    font-size:12px;
    height:500px;
}
    .menu > li {
        position: relative;
        cursor: pointer;
    }
        .menu > li > a {
            display: block;
            padding: 5px;
            color: white;
            text-decoration: none;
        }
        .menu > li:hover > a {
            color: #ccc;
        }
/* Submenu */
.submenu {
    display: none;
    position: absolute;
    left: 0;
    top: 31px;
    list-style: none;
    min-width: 250px;
    background: #055952;
    z-index: 10000 !important
}
    .submenu li {
        border-bottom: 1px solid #fff
    }
    .submenu li a {
        display: block;
        padding: 5px;
        color: white;
        text-decoration: none;
    }

        .submenu li a:hover {
            color: #ccc
        }

/* Hiển thị submenu khi hover */
.menu li:hover .submenu {
    display: block;
}

/* Responsive cho mobile */
@media (max-width: 768px) {
     
    .submenu {
        position: absolute;
        top:31px;
        display: none;
    }

    .menu li:hover .submenu {
        display: block;
    }
}