Answers for "how to use a media query in css"

media query min and max

/* Max-width */
@media only screen and (max-width: 600px)  {...}

/* Min-width */
@media only screen and (min-width: 600px)  {...}

/* Combining media query expressions */
@media only screen and (max-width: 600px) and (min-width: 400px)  {...}

media query

@media only screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}