<!DOCTYPE html>
<html lang="en-US">
<head>
<style>
input:default{
box-shadow: 0 0 3px 5px black;
}
</style>
</head>
<body>
<h1>CSS :default Selector</h1>
<input type="radio" name="car" value="bmw" checked> BMW<br>
<input type="radio" name="car" value="audi"> Audi<br>
<input type="radio" name="car" value="benz"> Benz
</body>
</html>