#back-to-top-arrow {
    position: fixed;
    bottom: 40px;
    right: 40px;
    display: none;
    font-size: 24px;
    background: black;
    color: #fff;
    padding: 10px 20px;
    border-radius: 50%;
    text-align: center;
    z-index: 1000;
    cursor: pointer;
    text-decoration: none;
    transition: opacity 0.3s, visibility 0.3s;
}

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