Responsive CSS

@media only screen and (max-width: 600px) {
  .example {background: red;}
}

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

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