<!DOCTYPE html>
<title>CSS Backdrop Filters Animation: Opacity Reference</title>
<link rel="author" title="Mason Freed" href="mailto:masonfreed@chromium.org">
<style>
    .square {
        position: absolute;
        width: 100px;
        height: 100px;
        top: 100px;
        left: 100px;
        background: black;
    }
    .filt {
        position: absolute;
        width: 200px;
        height: 200px;
        top: 50px;
        left: 50px;
        backdrop-filter: opacity(50%);
    }
    .greenbox {
        position: absolute;
        width: 50px;
        height: 50px;
        top: 75px;
        left: 75px;
        background: green;
    }
</style>
<p>You should see a blue square with a green box inside.</p>
<div class="square"></div>
<div class="filt">
    <div class="greenbox"></div>
</div>