* {
    padding: 0;
    margin: 0;
}

body {
    background-image:url("images/phone.jpg");
    background-size:cover;
    background-position:center;
}

#soondiv {
    width:100%;
    height:100vh;
    display:grid;
    place-items:end;
    mix-blend-mode:difference;
}

@media only screen and (min-width: 900px) {

  body {
    background-image:url("images/pc.jpg");
  }

  #soondiv {
    place-items: center;
  }

}