媒体查询，横竖屏

orientation

语法：

orientation：portrait | landscape

portrait：指定输出设备中的页面可见区域高度大于或等于宽度

landscape：除portrait值情况外，都是landscape

 1 @media screen and (orientation: portrait){
 2   .test::after {
 3     content: "竖屏";
 4   }
 5 }
 6 @media screen and (orientation: landscape){
 7   .test::after {
 8     content: "横屏";
 9   }
10 }