效果图：
1、首先创建html代码：
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<button>关注我</button>
</body>
</html>2、展示css3代码：
css
button{
width: 120px;
height: 38px;
background-color: transparent;
color: #000;
border: none;
border-radius: 5px;
cursor: pointer;
font-size: 20px;
font-weight: 600;
font-family: Arial, Helvetica, sans-serif;
box-sizing: border-box;
position: relative;
transition: all 0.6s ease-in-out;
}
button:after{
content: '';
position: absolute;
top: 0;
left: 0;
width: 1px;
height: inherit;
background-color: #333;
z-index: -1;
transition: all 0.6s ease-in-out;
}
button:hover{
color: aliceblue;
cursor: pointer;
}
button:hover:after{
width: 100%;
border-radius: 6px;
}本人也是学习阶段，希望能够一起学习，高手请留余地勿喷。