1. <!DOCTYPE html>
    2. <html lang="zh-CN">
    4. <head>
    5.   <meta charset="UTF-8">
    6.   <meta http-equiv="X-UA-Compatible" content="IE=edge">
    7.   <meta name="viewport"
    8.     content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum=1.0, user-scalable=no">
    9.   <title>三角形</title>
    10.   <link rel="stylesheet" href="index.css">
    11. </head>
    13. <body>
    14.   <div></div>
    15. </body>
    17. </html>
    div {
  width: 0;
  height: 0;
  border: 10px solid transparent;
  border-left-color: skyblue;
}

    image.png