CSS-三角形及其原理

CSS中三角形在网页中比较常见，以前是图片，不过现在基本上都是通过CSS可以完成，实现比较简单，我们可以看一组简单的三角形效果:

其实实现起来比较简单，通过空div然后设置宽高为0，之后可以四周border的宽度，控制三角形的形状，四个border可以看成是两横横竖的木头的重叠的效果，两横在两竖上面，三角形就是中间重叠的部分切分出来的,样式的代码如下:

.triangle {
        width: 0;
        height: 0;
        border-top: 20px solid #EEB422;
        border-right: 20px solid #C0FF3E;
        border-bottom: 20px solid #A020F0;
        border-left: 20px solid #7CFC00;
    }

    .triangle-up {
        width: 0;
        height: 0;
        border-right: 20px solid transparent;
        border-bottom: 40px solid #A020F0;
        border-left: 20px solid transparent;
    }

    .triangle-down {
        width: 0;
        height: 0;
        border-top: 40px solid #EEB422;
        border-right: 20px solid transparent;
        border-left: 20px solid transparent;
    }

    .triangle-left {
        width: 0;
        height: 0;
        border-top: 20px solid transparent;
        border-bottom: 20px solid transparent;
        border-left: 40px solid #7CFC00;
    }

    .triangle-right {
        width: 0;
        height: 0;
        border-top: 20px solid transparent;
        border-bottom: 20px solid transparent;
        border-right: 40px solid #C0FF3E;
    }

    .triangle-left-bottom {
        width: 0;
        height: 0;
        border-top: 40px solid transparent;
        border-left: 40px solid #7CFC00;
    }

    .triangle-right-bottom {
        width: 0;
        height: 0;
        border-top: 40px solid transparent;
        border-right: 40px solid #C0FF3E;
    }

具体的html页面代码:

<div class="row">
        <span>四个三角</span>
        <div class="triangle">
        </div>
    </div>
    <div class="row">
        <span>上三角</span>
        <div class="triangle-up">
        </div>
    </div>
    <div class="row">
        <span>下三角</span>
        <div class="triangle-down">
        </div>
    </div>
    <div class="row">
        <span>左三角</span>
        <div class="triangle-left">
        </div>
    </div>
    <div class="row">
        <span>右三角</span>
        <div class="triangle-right">
        </div>
    </div>
    <div class="row">
        <span>左下角</span>
        <div class="triangle-left-bottom">
        </div>
    </div>
    <div class="row">
        <span>右下角</span>
        <div class="triangle-right-bottom">
        </div>
    </div>

参考：http://www.tuicool.com/articles/qYjaMjA