<!DOCTYPE html>
<html>
<head>
<title>CSS Motion Path Referecne: url() with border-box</title>
<style>
#outer {
width: 300px;
height: 100px;
padding: 50px;
border: 50px solid black;
}
#target {
width: 50px;
height: 50px;
background-color: green;
transform: translate(25px, -25px);
border-radius: 50% 50% 0 0;
}
</style>
</head>
<body>
<div id="outer">
<div id="target"></div>
</div>
</body>
</html>