通过css的border 可以绘制出三角形, 不同的样式组合，有着不同的效果，可以控制它的大小，颜色，方向。看下面各种图形，相信可能还有很多图形，大家都没见过。
先写出公共的样式：
<span style="color: #008080;">1</span> <span style="color: #800000;">.border </span>{
<span style="color: #008080;">2</span> <span style="color: #ff0000;"> width</span>:<span style="color: #0000ff;"> 0</span>;
<span style="color: #008080;">3</span> <span style="color: #ff0000;"> height</span>:<span style="color: #0000ff;"> 0</span>;
<span style="color: #008080;">4</span>
<span style="color: #008080;">5</span> <span style="color: #ff0000;"> border-color</span>:<span style="color: #0000ff;"> transparent</span>;
<span style="color: #008080;">6</span> <span style="color: #ff0000;"> border-width</span>:<span style="color: #0000ff;"> 1rem</span>;
<span style="color: #008080;">7</span> <span style="color: #ff0000;"> border-style</span>:<span style="color: #0000ff;"> solid</span>;
<span style="color: #008080;">8</span> }
在上面的css基础上，添加下面的组合代码，将可以控制三角形的方向：
<span style="color: #008080;">1</span> <span style="color: #800000;">border-left-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-right-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-top-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-bottom-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-bottom-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-right-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-bottom-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-right-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-top-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-top-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-top-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-bottom-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-right-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-top-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">3</span> <span style="color: #800000;">border-bottom-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-top-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">3</span> <span style="color: #800000;">border-right-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-bottom-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">3</span> <span style="color: #800000;">border-right-color: #000;</span>
<span style="color: #008080;">1</span> <span style="color: #800000;">border-top-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-right-color: #000; </span><span style="color: #008080;">3</span> <span style="color: #800000;">border-bottom-color: #000;</span>
还有下面的这个效果，
<span style="color: #008080;">1</span> <span style="color: #800000;">border-left-color: #000; </span><span style="color: #008080;">2</span> <span style="color: #800000;">border-right-color: #000; </span><span style="color: #008080;">3</span> <span style="color: #800000;">border-left-width: 3rem;</span>
不同的组合产生不同的效果，大家可以尝试各种组合带来的效果。
