.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%;
}