#bottone-indietro {
    position: fixed;
    bottom: 20px;
    right: 20px;
    padding: 12px 18px;
    background: black;
    color: white;
    border: none;
    border-radius: 20px;
    cursor: pointer;
    font-size: 16px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.3);
}