css实现倒三角

[code]width: 40px;height: 40px;border: 40px;border-style: solid;border-color: red green blue brown;

三角形:

[code]width: 0;height: 0;border: 50px;border-style: solid;border-color: red green blue brown;

倒三角就是把其他边取消掉

[code]width: 0;height: 0;border: 50px;border-style: solid;border-color: red transparent transparent transparent;