CSS 三角制作

如图

结构

<div class="box1"></div>
<div class="box2"></div>
<div class="jd">
    <span></span>
</div>

css

<style>
    .box1 {
        width: 0;
        height: 0;
        /* border: 10px solid pink; */
        border-top: 10px solid pink;
        border-right: 10px solid red;
        border-bottom: 10px solid blue;
        border-left: 10px solid green;
    }
    .box2 {
        width: 0;
        height: 0;
        border: 10px solid transparent;
        border-left-color: pink;
		border-top-color: pink;
		border-right-color: pink;
		/* border-bottom-color: pink; */
        margin: 100px auto;
    }
    .jd {
        position: relative;
        width: 120px;
        height: 249px;
        background-color: pink;
    }
    .jd span {
        position: absolute;
        right: 15px;
        top: -10px;
        width: 0;
        height: 0;
        /* 为了照顾兼容性 */
        line-height: 0;  
        font-size: 0;
        border: 5px solid transparent;
        border-bottom-color: pink;
    }
</style>