#page_top{
  width: 50px;
  height: 50px;
  position: fixed;
  right: 20px;
  bottom: 20px;
  background: #043D78;
  line-height: 1;
  border-radius: 50%;
  background-color: rgba(41, 63, 128, 0.51);
}
#page_top a{
  position: relative;
  display: block;
  width: 50px;
  height: 50px;
  text-decoration: none;
}

#page_top a:hover {
    background-color: #043D78;
    text-decoration: none;
    border-radius: 50%;
    opacity:0.5;
}

#page_top a::before{
  content: "";
  display: block;
  position: absolute;
  top: 45%;
  left: 43%;
  width: 8px;
  height: 8px;
  border-top: 2px solid #fff;
  border-left: 2px solid #fff;
  transform: rotate(45deg) translateY(-50%);
  transform-origin: 0 0;
}

@media screen and (max-width: 768px) {
  #page_top{
    right: 10px;
    bottom: 10px;
  }
}