<!DOCTYPE html>
<style>
div {
    position: absolute;
}

#bottom-backdrop {
    top: 100px;
    left: 100px;
    height: 300px;
    width: 300px;
    background-color: rgb(0, 50, 0);
}

#bottom {
    top: 125px;
    left: 125px;
    height: 250px;
    width: 250px;
    background-color: rgb(0, 90, 0);
}

#middle-backdrop {
    top: 150px;
    left: 150px;
    height: 200px;
    width: 200px;
    background-color: rgb(0, 130, 0);
}

#middle {
    top: 175px;
    left: 175px;
    height: 150px;
    width: 150px;
    background-color: rgb(0, 170, 0);
}

#top-backdrop {
    top: 200px;
    left: 200px;
    height: 100px;
    width: 100px;
    background-color: rgb(0, 210, 0);
}

#top {
    top: 225px;
    left: 225px;
    height: 50px;
    width: 50px;
    background-color: rgb(0, 255, 0);
}
</style>
<body>
Test for dialog::backdrop stacking order. The test passes if there are 6
boxes enclosed in each other, becoming increasingly smaller and brighter
green.
<div id="bottom-backdrop"></div>
<div id="bottom"></div>
<div id="middle-backdrop"></div>
<div id="middle"></div>
<div id="top-backdrop"></div>
<div id="top"></div>
</body>
