青年时鲁莽,老年时悔恨——富兰克林

代码如下:

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<!DOCTYPE html>
<html lang="en">

<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.triangle {
width: 0;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-bottom: 100px solid red;
}
</style>
</head>

<body>
<div class="triangle"></div>
</body>

</html>

效果如下:

image-20230224205342476

如果我们需要让三角形的箭头朝右,可以给一个旋转属性

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.triangle {
width: 0;
height: 0;
border-left: 50px solid transparent;
border-right: 50px solid transparent;
border-bottom: 100px solid red;
transform: rotate(90deg);
}

效果

image-20230224205459189