<script>
if (window.internals)
    internals.settings.setConstantPropertiesEnabled(true);
</script>
<style>
div {
    position: absolute;
    left: 100px;
    top: 100px;
    width: 100px;
    height: 100px;
    background-color: green;

    top: env(safe-area-inset-top);
    left: env(safe-area-inset-left);
}
</style>
<body>
<div></div>
<p>The box should be at 0, 0.</p>