要选择所有元素，请使用* CSS选择器。您可以尝试运行以下代码以选择所有元素，
<!DOCTYPE html>
<html>
<head>
<style>
*{
color: blue;
background-color: orange;
}
</style>
</head>
<body>
<h1>Demo Website</h1>
<h2>Learning</h2>
<p id = "tutorials">Tutorials on web dev, programming, database, networking, etc.</p>
<p>Every tutorials has lessons with illustrations and figures.</p>
</body>
</html>