响应式布局

/* xs up */

@media only screen {}/* small up */

@media only screen and (min-width: 40.063em) {}/* medium up */

@media only screen and (min-width: 64.063em) {}/* large up */

@media only screen and (min-width: 90.063em) {}/* xlarge up */

@media only screen and (min-width: 120.063em) {}