w3 scholls mobile first code example

Example 1: media query

/* Extra small devices (phones, 600px and down) */
@media only screen and (max-width: 600px) {}

/* Small devices (portrait tablets and large phones, 600px and up) */
@media only screen and (min-width: 600px) {}

/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {}

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {}

/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) {}

Example 2: media query

@media (max-height : 800px){ /* from 0 to 800 px max height applies */
  p{
    font-size:10px
  }
}