body {
    background-image: url('imgs/light1.jpg');
    /*background-image: url('https://cdn.pixabay.com/photo/2018/01/24/17/33/light-bulb-3104355_1280.jpg');*/
    background-position: center center;
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-size: cover;
} 
@media only screen and (max-width: 767px) {
    body {
        background-image: url('imgs/light1.jpg');
        /*background-image: url('https://cdn.pixabay.com/photo/2018/01/24/17/33/light-bulb-3104355_1280.jpg');*/
    }
}