z-index 及透明度
z-index
图层
默认是0，最高无限
.box{
position: relative;
}
div:nth-of-type(1){
width: 200px;
height: 200px;
background: #c3d23b;
border: 1px solid #c3d23b;
border-radius: 30px;
z-index: 999;
}
透明度
opacity ： 0.5 背景透明度（0~1）
html：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>index</title>
<link rel="stylesheet" href="../z-index及透明度/style.css">
</head>
<body>
<div class="box">
<div></div>
<div>琪琪又炸毛了</div>
</div>
</body>
</html>
css：
div:nth-of-type(1){
width: 200px;
height: 200px;
background: #c3d23b;
border: 1px solid #c3d23b;
border-radius: 30px;
}
div:nth-of-type(2){
width: 102px;
height: 20px;
color: #2f70ff;
background: #d9deea;
border: 1px solid #2f70ff;
position: relative;
top: -50px;
right: -20px;
opacity: 0.5;
}