快速的画一个三角形

1.向下的三角形

width: 0;

height: 0;

border-left: 10px solid transparet;

border-right: 10px solid transparet;

border-top: 10px solid red;

2.向上的三角形

width: 0;

height: 0;

border-left: 10px solid transparet;

border-right: 10px solid transparet;

border-bottom: 10px solid red;

3.向左的三角形

width: 0;

height: 0;

border-top: 10px solid transparet;

border-bottom: 10px solid transparet;

border-right: 10px solid red;

4.向右的三角形

width: 0;

height: 0;

border-top: 10px solid transparet;

border-bottom: 10px solid transparet;

border-left: 10px solid red;