    <style>
        body { font-family: Arial, sans-serif; margin: 0; padding: 0; background: #f8f8f8; }
        header { background: #2e7d32; color: white; padding: 10px; text-align: center; }
        nav { background: #388e3c; padding: 10px; text-align: center; }
        nav a { color: white; text-decoration: none; padding: 10px; display: inline-block; }
        nav a:hover { background: #66bb6a; }
        .content { padding: 20px; }
        .hidden { display: none; }
    </style>
