<!DOCTYPE html>
<html>
<head>
<style>
.backdrop {
    position: absolute;
    top: 100px;
    left: 100px;
    height: 100px;
    width: 100px;
    background-color: green;
}
</style>
</head>
<body>
Test dynamic changes to ::backdrop style. The test passes if there is a green box below.
<div class="backdrop"></div>
</body>
</html>