/* Extra small devices (portrait phones, less than 576px) */
@media (max-width: 575px) { ... }

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) and (max-width: 767px) { ... }

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) and (max-width: 991px) { ... }

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) and (max-width: 1199px) { ... }

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) and (max-width: 1439px) { html{ font-size: 16px} }
@media (min-width: 1440px) { html{ font-size: 18px} }