#back-to-top {
    line-height: 14px;
    padding: 10px;
    border-radius: 5px;
    font-size: 12px;
    position: fixed;
    bottom: 10px;
    right: 10px;
    z-index: 9999;
    text-align: center;
    background: #f5f5f5;
    color: gray;
    cursor: pointer;
    border: 1px solid gray;
    text-decoration: none;
    transition: opacity 0.2s ease-out;
    opacity: 0;
  }
  #back-to-top:hover {
    background: #e5e5e5;
    transition: opacity 0.2s ease-out;
  }
  #back-to-top.show {
    opacity: 0.75;
  }
  #back-to-top.show:hover {
    opacity: 1;
    transition: opacity 0.2s ease-out;
  }