<!DOCTYPE html>
<meta charset="utf-8">
<title>Background Clip Follows Rounded Corner</title>
<link rel="match" href="reference/background-rounded-image-clip.html">
<link rel="help" href="https://drafts.csswg.org/css-backgrounds-3/#corner-clipping">
<style>
    html {
        background-color: green;
    }
    #a {
        top: 20px;
        left: 20px;
        position: absolute;
        width: 20px;
        height: 20px;
        background-color: black;
    }

    #b {
        position: absolute;
        width: 300px;
        height: 200px;
        background-image: linear-gradient(green, green);
        background-clip: content-box;
        border-top-left-radius: 90px;
        border-width: 10px;
        border-style: solid;
        border-color: transparent;
    }
</style>
<div id="a"></div>
<div id="b"></div>