用纯Css创建三角形

箭头朝上

代码如下:

#triangle-up {

    width: 0;

    height: 0;

    border-left: 50px solid transparent;

    border-right: 50px solid transparent;

    border-bottom: 100px solid red;

}

箭头朝下

代码如下:

#triangle-down {

    width: 0;

    height: 0;

    border-left: 50px solid transparent;

    border-right: 50px solid transparent;

    border-top: 100px solid red;

}

箭头朝左

代码如下:

#triangle-left {

    width: 0;

    height: 0;

    border-top: 50px solid transparent;

    border-right: 100px solid red;

    border-bottom: 50px solid transparent;

}

箭头朝右

代码如下:

#triangle-right {

    width: 0;

    height: 0;

    border-top: 50px solid transparent;

    border-left: 100px solid red;

    border-bottom: 50px solid transparent;

}