请找到这个 css 类来创建简单的 uparrow downarrow 左箭头和右箭头。
<html>
<style>
.left {border-bottom: 10px solid transparent;
border-right: 10px solid red;
border-top: 9px solid transparent;
float: left;}
.right {border-bottom: 10px solid transparent;
border-left: 10px solid red;
border-top: 9px solid transparent;
float: left;}
.top{ border-color: black transparent transparent;
border-style: solid;
border-width: 11px 7px 10px;
float: left;}
.bottom {border-color: transparent transparent black !important;
border-style: solid;
border-width: 0 27px 19px 25px;
float: right;}
</style>
<div class="left"></div>
<div class="right"></div>
<div class="top"></div>
<div class="bottom"></div>
</html>
左类意味着向左箭头。,请任何人建议我使用简单的css创建箭头的更好方法