footer {
  background-color:var(--footer-back);
  color:var(--footer-color);
  background-image:url(../image/resource/thumb_footer_bg.jpg);
  background-size:cover;background-position:left center;
}
@media screen and (min-width:641px) and (max-width:835px) {
  footer {
    background-color:var(--footer-back);
    color:var(--footer-color);
    background-image:url(../image/resource/thumb_footer_bg.jpg);
  }
}
@media screen and (max-width:640px) {
  footer {
    background-color:var(--footer-back);
    color:var(--footer-color);
    background-image:url(../image/resource/thumb_footer_bg.jpg);
  }
}