.btn-circle.btn-md {
    width: 50px;
    height: 50px;
    padding: 5px 11px;
    border-radius: 50%;
    font-size: 24px;
    text-align: center;
}

.btn-circle.btn-lg {
    width: 100px;
    height: 100px;
    padding: 13px 18px;
    border-radius: 60px;
    font-size: 15px;
    text-align: center;
}

#btn-back-to-top-old {
  position: fixed;
  display: none;
  bottom: 20px;
  right: 20px;
  z-index: 99;

  width: 50px;
  height: 50px;
  padding: 5px 11px;
  border-radius: 50%;
  font-size: 24px;
  line-height: 1.33;
}