.button-up{
  position:fixed;
  bottom:.5%;
  right:63px;
  display:flex;
  justify-content:center;
  align-items:center;
  width:40px;
  height:40px;
  cursor:pointer;
  border:1px solid var white;
  color:white;
  background:#408ab4;
  transition:opacity .3s;
  opacity:0;
  z-index:-100;
}
.button-up.active{
  opacity:1;
  z-index:10000;
}