CSS利用border绘制图性

绘制梯形

width:10px;

border-top:10px solid red;

border-right:10px solid transparent;

border-left:10px solid transparent;

border-bottom:10px solid transparent;

绘制三角形：

width:0px;

border-top:10px solid red;

border-right:10px solid transparent;

border-left:10px solid transparent;

border-bottom:10px solid transparent;

绘制直角三角形：

width:0px;

border-top:20px solid red;

border-right:0px solid transparent;

border-left:10px solid transparent;

border-bottom:10px solid transparent;