.back-to-top-button {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 45px;
    height: 45px;
    background-color: #000;
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.3s ease, transform 0.3s ease;
    z-index: 9999;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  }
  
  .back-to-top-button.visible {
    opacity: 1;
    transform: translateY(0);
  }
  
  .back-to-top-button:hover {
    background-color: #222;
    transform: translateY(-3px);
  }
  
  @media (max-width: 768px) {
    .back-to-top-button {
      width: 40px;
      height: 40px;
      bottom: 20px;
      right: 20px;
    }
}