body   
    {
        
        background-image: 
            url(https://www.desktopbackground.org/download/o/2010/05/03/11638_ultra-hd-4k-google-wallpapers-hd-desktop-backgrounds-3840x2400_3840x2400_h.jpg);
        background-size: 100%;

    }
#main-form
    {
        margin: 20px;
    }

#image-form
    {
        margin: 20px;
    }
#lucky-form
    {
        margin: 20px;
    }