/* Reset */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* Menu chính */
#menu {
    list-style: none;
    width: 150px;
}

/* Item */
#menu li {
    position: relative;
}

/* Link */
#menu li a {
    display: block;
    padding: 10px;
    color: #fff;
    background: #000000;
    text-decoration: none;
    border-bottom: 1px solid #fff;
}

/* Hover */
#menu li a:hover {
    background: darkgray;
}

/* Menu cấp 2 & 3 */
#menu ul {
    display: none;
    position: absolute;
    top: 0;
    left: 150px; /* xổ sang phải */
    list-style: none;
    width: max-content;
}

/* Hiện menu con khi hover */
#menu li:hover > ul {
    display: block;
}