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<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>CSS HWaccel</title>
        <meta name=viewport content="width=device-width,initial-scale=1">
    </head>
    <style>
body {
    background: white;
}

#a {
    transition: transform 1s;
    margin-left: 50%;
    transform: translateY(0) translateZ(0);
}
#a.down {
    transform: translateY(200px) translateZ(0);
}
    </style>
    <body>
        <div id="a">Hello World</div>

        <script>
var x = document.getElementById("a");

setInterval(() => {
    x.className = x.className == "down" ? "" : "down";
    console.log(x.className);
}, 2000);
        </script>
    </body>
</html>