要为不同的CSS样式规则设置媒体查询，您可以尝试运行以下代码-
<html>
<head>
<style>
body {
background-color: lightpink;
}
@media screen and (max-width: 420px) {
body {
background-color: lightblue;
}
}
</style>
</head>
<body>
<p>If screen size is less than 420px, then it will show lightblue color, or else it will show light pink color</p>
</body>
</html>