CSS media query

CSS media query:

/* Larger than mobile */
@media (min-width: 400px) { /* specific rules go here */ }

/* Larger than phablet */
@media (min-width: 550px) { /* specific rules go here */ }

/* Larger than tablet */
@media (min-width: 750px) { /* specific rules go here */ }

/* Larger than desktop */
@media (min-width: 1000px) { /* specific rules go here */ }

/* Larger than Desktop HD */
@media (min-width: 1200px) { /* specific rules go here */ }

• Viewport Sizer - Devices

Have your breakpoints make sense for your design!!
Start with one breakpoint.