先看下效果图：
再看下源码
<!DOCTYPE html>
<html class="no-js">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<title></title>
<meta name="description" content="" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="stylesheet" href="" />
<style>
.comment {
height: 20px;
width: 25px;
background: #8593b0;
position: relative;
cursor: pointer;
display: flex;
justify-content: center;
}
.comment::before {
content: '';
border: 5px solid transparent;
border-right: 5px solid #8593b0;
position: absolute;
top: 5px;
left: -10px;
}
span {
color: #f8f8f8;
font-size: 30px;
line-height: 20px;
position: absolute;
top: -10px;
}
</style>
</head>
<body>
<div class="comment">
<span>..</span>
</div>
</body>
</html>