.button_top {
  background-color: #085;
  color: white;
  font-size: 16px;
  width: 60px;
  height: 60px;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  transition: .3s;
  opacity: 0.5;
  position: fixed;
  bottom: 10px;
  right: 10px;
}
.button_top::before {
  content: "";
  display: block;
  width: 10px;
  height: 10px;
  border-top: 2px solid white;
  border-right: 2px solid white;
  transform: rotate(-45deg);
}