tip:
1.css默认手机样式，平板在此基础上修改数值；
2.以500px作为两者区分
1.手机css
h3{height: 4.96rem;padding-top: 1.51rem;font-size: 1rem;font-weight: 500;text-align: center;}
2.平板css
2.1竖屏@media screen and (orientation: portrait) and (min-device-width: 500px){h3{padding-top: 1.28rem;height: 3.38rem;font-size: .75rem;}}
2.2横屏
@media screen and (orientation: landscape) and (min-device-width: 500px){h3{padding-top: .45rem;height: 1.93rem;font-size: .6rem;}}
