<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>画三角形</title>
<style>
.triggle{
width: 0px;
height: 0px;
border-width: 100px;
border-style: dotted dotted solid dotted;
border-color: transparent transparent red transparent;
}
</style>
</head>
<body>
<div class="triggle"></div>
</body>
</html>
前端小技巧：边框写三角形