Responsive background image

styles.css

html{
  width: 100vw; height: 100vh;
}

body {
  width: 100vw;
  height: 100vh;
  /*Replace with some_image with image url/path*/
  background: url("some_image.png");
  background-repeat: no-repeat;
  background-position: center;
  background-size: cover;
}