.gotoBottomBtn {
  position: fixed;
  bottom: 10%;
  left: 20%;
  z-index: 9;
  font-size: 18px;
  border: none;
  outline: none;
  color: white;
  cursor: pointer;
  padding: 15px;
  border-radius: 4px;
}

.gotoBottomBtn_back {
  position: fixed;
  bottom: 10%;
  left: 31%;
  z-index: 9;
  font-size: 18px;
  border: none;
  outline: none;
  color: white;
  cursor: pointer;
  padding: 15px;
  border-radius: 4px;
}

  .nextButton {
    position: absolute;
    font-size: 1.5em;
    text-transform: uppercase;
    padding: 7px 20px;
    left: 50%;
    width: 200px;
    top: 50%;
    border-radius: 10px;
    color: white;
    text-shadow: -1px -1px 1px rgba(0,0,0,0.8);
    border: 5px solid transparent;
    border-bottom-color: rgba(0,0,0,0.35);
    background-color: #f39c12;
    cursor: pointer;

    animation: pulse 1s infinite alternate;
    transition: background 0.4s, border 0.2s, margin 0.2s;
  }
  .nextButton:hover {
    background: hsla(220, 100%, 60%, 1);
    margin-top: -1px;

    animation: none;
  }
  .nextButton:active {
    border-bottom-width: 0;
    margin-top: 5px;
  }
  @keyframes pulse {
    0% {
      margin-top: 0px;
    }
    100% {
      margin-top: 6px; 
    } 
  }