[data-slides] {
    background-image: url(images/slider-1.jpg); /* Default image. */
    background-repeat: no-repeat;
    background-position: center top;
    background-size: cover;
    transition: background 1s linear;
}

/* Use additional CSS to control the `height` of `[data-slides]`, like so: */

.test {
  height: 385px;
  border: 1px solid black;
}
@media all and (min-width: 48em) {
    .test { height: 385px; }
}