div css下拉三级菜单

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS三级下拉菜单</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        body {
            font-family: Arial, sans-serif;
        }
        .menu {
            list-style: none;
            background-color: #333;
            display: flex;
            justify-content: center;
        }
        .menu li {
            position: relative;
        }
        .menu a {
            display: block;
            padding: 10px 20px;
            color: #fff;
            text-decoration: none;
        }
        .menu li:hover > ul {
            display: block;
        }
        .menu ul {
            display: none;
            position: absolute;
            top: 100%;
            left: 0;
            background-color: #333;
            list-style: none;
        }
        .menu ul li {
            width: 200px;
        }
        .menu ul ul {
            top: 0;
            left: 100%;
        }
    </style>
</head>
<body>
    <ul class="menu">
        <li><a href="#">菜单1</a>
            <ul>
                <li><a href="#">子菜单1-1</a></li>
                <li><a href="#">子菜单1-2</a>
                    <ul>
                        <li><a href="#">子菜单1-2-1</a></li>
                        <li><a href="#">子菜单1-2-2</a></li>
                    </ul>
                </li>
            </ul>
        </li>
        <li><a href="#">菜单2</a></li>
        <li><a href="#">菜单3</a></li>
    </ul>
</body>
</html>