<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <script>
    function hangFor(ms) {
        const startTime = Date.now();
        while (1) {
            if (Date.now() - startTime > ms)
                break;
        }
    }

    function setBodyHeight(height) {
        document.body.style.height = `${height}px`;
    }
    </script>
    <style>
        html, body {
            overflow: hidden;
        }
    </style>
</head>
<body>
</body>
</html>