效果如图↑
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>body {
background: #eeeff2;
}
/*左上角标签，父元素必须设置position: relative;overflow: hidden;height: 大于150;width: 大于150px;，同时，角标标签内加入属性superscript-title="左上角标签文字内容"*/
.subscript:after {
position: absolute;
top: 15px;
left: -45px;
width: 150px;
height: 30px;
content: attr(superscript-title);
text-align: center;
font-size: 14px;
color: white;
line-height: 30px;
font-family: 'Microsoft YaHei', 'PingFangSC-Regular', 'sans-serif', 'San Francisco', 'Microsoft Sans Serif', 'Arial'; /*背景旋转角度渐变*/
background: -webkit-linear-gradient(90deg, orange 0%, orangered 100%); /* Safari 5.1 - 6.0 */
background: -o-linear-gradient(90deg, orange 0%, orangered 100%); /* Opera 11.1 - 12.0 */
background: -moz-linear-gradient(90deg, orange 0%, orangered 100%); /* Firefox 3.6 - 15 */
background: linear-gradient(90deg, orange 0%, orangered 100%); /* 标准的语法（必须放在最后） *//*旋转角标*/
-moz-transform: rotate(-45deg);
-webkit-transform: rotate(-45deg);
-o-transform: rotate(-45deg);
-ms-transform: rotate(-45deg);
transform: rotate(-45deg);
}
/*时下流行的风格--【新拟态】________________________*/
.subscript {
position: relative;
overflow: hidden;
font-family: 'Arial';
margin: 100px;
border-radius: 40px;
width: 200px;
height: 200px;
box-shadow: 0 20px 55px rgba(0, 0, 0, 0.1), -10px -10px 15px rgba(255, 255, 255, 0.9);
background: linear-gradient(-180deg, #eee, #f9f9f9);
}
/*渐变文字样式________________________*/
.subscript p {
margin: 0;
padding: 0;
line-height: 200px;
font-size: 100px;
text-align: center;
color: #238aea;
/*渐变文字（仅谷歌内核浏览器支持）*/
background: -webkit-linear-gradient(0deg, #1858f1, #32c0e3);
-webkit-background-clip: text;
-webkit-text-fill-color: transparent;
}
</style>
</head>
<body>
<div class="subscript" superscript-title="标签内容">
<p>Aa</p>
</div>
</body>
</html>
