PC端 / Ipad/ 手机端
屏幕大于1920px的时候
@media only screen and (min-width: 1920px) {}
屏幕1920px-1200px之间的时候
@media only screen and(max-width: 1920px) and (min-width: 1200px) {}
屏幕992px-1200px之间的时候
@media only screen and (max-width: 1200px) and (min-width: 992px) {}
屏幕768px-992px之间的时候
@media only screen and (max-width: 992px) and (min-width: 768px) {}
屏幕小于768px
@media only screen and (max-width: 768px) {}