<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>三角△</title>
<style>
*{
padding: 0;
margin: 50px;
}
div{
position: relative;
width: 249px;
height: 35px;
border: 1px solid #000;
}
div::after {
content: "";
position: absolute;
top: 8px;
right: 15px;
width: 10px;
height: 10px;
border-right: 1px solid #000;
border-bottom: 1px solid #000;
transform: rotate(45deg);
transition: all 0.2s;
}
div:hover::after {
transform: rotate(225deg);
}
<×yle>
</head>
<body>
<div></div>
</body>
<cml>