<html>

<head>
    <style>
        html {
            font-size: 30px;
        }
        
        h1 {
            font-size: 2rem;
        }
    </style>
</head>

<body>
    <div>
        <p>Normal text</p>
        <h1>2rem text</h1>
    </div>
</body>

</html>