tiled-radial-gradients-ref.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<style>
body {
margin: 0px;
}
#outer {
position: absolute;
width: 600px;
height: 200px;
background-color: aquamarine;
}
#left, #right {
position: absolute;
width: 300px;
height: 200px;
background-image: radial-gradient(closest-side, red 40%, transparent 40%)
}
#left {
left: 80px;
}
#right {
left: 380px;
}
</style>
</head>
<body>
<div id="outer">
<div id="left"></div>
<div id="right"></div>
</div>
</body>
</html>