.back-to-top {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 9999;
    font-size: 18px;
    background-color: #333;
    color: #fff;
    cursor: pointer;
    padding: 15px;
    border-radius: 50%;
}

.back-to-top:hover {
    background-color: #555;
}