challenge css 2.html

<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="box123.css">
</head>
<body>
    <!--made in 12minutes -->
    <div class="container">
        <div class="box1">
            <div class="box2">
                <div class="box3"></div>
            </div>
        </div>
    
    </div>
    
</body>
</html>