Variables and Custom Properties in CSS .html

<!DOCTYPE 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>Variables and Custom Properties</title>
    <style>
        :root{
            --primary-color:blue;
            --danger-color:orange;
            --maxw:333px;
        }
        .box {
    width: 200px;
    height: 200px;
    background-color: var(--primary-color);
    box-shadow: 3px 3px var(--danger-color);
    padding: 15px;
    border: 13px solid red;
}
        .container{
    display: flex;
    margin: -18px 60px;
    padding: 322px;
    max-width: var(--maxw);
}
    </style>
</head>
<body>
    <div class="container">
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
    </div>
    
</body>
</html>