/*SP幅背景調整*/
@media screen and (max-width: 768px) {
body:before{
  content:"";
  display:block;
  position:fixed;
  top:0;
  left:0;
  z-index:-1;
  width:100%;
  height:100vh;
  background:url(https://www.hiroshima-palette.com/upload/back_image/29.jpg) left top no-repeat;
  background-size:cover;
}
}