ehzhang/prince-pseudoclass-z-index.html

## prince-pseudoclass-z-index.html
<html>
  <head>
    <style>
      * {
        box-sizing: border-box;
      }

      .item {
        display: inline-block;
        width: 20px;
        height: 20px;
        position: relative;
        background: red;
      }

      .item::before {
        content: '';
        position: absolute;
        top: 10px;
        left: 10px;
        width: 20px;
        height: 20px;
        background: blue;
        z-index: -1;
      }

    </style>
  </head>
  <body>
    <div class="item"></div>
  </body>
</html>
	<html>
	<head>
	<style>
	* {
	box-sizing: border-box;
	}

	.item {
	display: inline-block;
	width: 20px;
	height: 20px;
	position: relative;
	background: red;
	}

	.item::before {
	content: '';
	position: absolute;
	top: 10px;
	left: 10px;
	width: 20px;
	height: 20px;
	background: blue;
	z-index: -1;
	}

	</style>
	</head>
	<body>
	<div class="item"></div>
	</body>
	</html>