body div {
    width: 100%;
    height: 100%;
    background:url(screen.JPG) center center no-repeat;
}

/* Smartphones (portrait and landscape) ----------- */
@media only screen and (min-device-width : 320px) and (max-device-height: 736px) {
body div {background-size: 66%;}
}
    
/* iPads (portrait and landscape) ----------- */
@media only screen and (min-device-width : 768px) and (max-device-width : 1024px) {
body div {background-size: 50%;}
}

/* Desktops and laptops ----------- */
@media only screen  and (min-width : 1224px) {
body div {background-size: 33%;}
}

/* Large screens ----------- */
@media only screen  and (min-width : 1824px) {
body div {background-size: 25%;}
}