#back-to-top{
  position:fixed;
  right:max(22px,calc((100vw - 1280px)/2 - 54px));
  bottom:28px;
  z-index:40;
  display:none!important;
  border:1px solid #ffd3a4;
  border-radius:20px;
  padding:8px 12px;
  background:#fff7ef;
  color:#ef7800;
  font:12px/1.2 "Microsoft YaHei UI","Microsoft YaHei",sans-serif;
  cursor:pointer;
  box-shadow:0 4px 14px rgba(0,0,0,.08);
}
#back-to-top.show{display:block!important}
#back-to-top:hover{background:#ff8200;color:#fff;border-color:#ff8200}
@media(max-width:900px){
  #back-to-top{right:16px;bottom:18px;padding:8px 10px}
}