<!DOCTYPE html>
<html lang="en">
<head>
<style>
.box {
position: absolute;
height: 50px;
width: 100px;
left: 20px;
background-color: black;
outline: 4px solid gray;
filter: invert(1);
}
</style>
</head>
<body>
<!-- You should see an outlined white rectangle with a black one beneath it. -->
<div class="box">
<div class="box" style="top: 60px; left: 0"></div>
</div>
</body>
</html>