To create a circle with radial gradient, you can try to run the following code. Set another parameter in radial gradient for shapes like circle
Example
<!DOCTYPE html>
<html>
<head>
<style>
#demo {
height: 400px;
background: radial-gradient(circle, red , blue, yellow);
}
</style>
</head>
<body>
<h2>Radial Gradient</h2>
<div id = "demo">Radial Gradients</div><br>
</body>
</html>