.isosceles{ width: 0; height: 0; border:30px solid; border-left-color: transparent; border-right-color: transparent; border-top-color: transparent; border-bottom-color: red;}
2.直角三角形
.right{ width: 0; height: 0; border:30px solid; border-left: 0; border-right-color: transparent; border-top: 0; border-bottom-color: red;}
3.圆
.round{ width: 100px; height: 100px; background-color: red; border-radius:50%; }
4.椭圆
.ellipse{ width: 100px; height: 80px; background-color: red; border-radius:50%; }