#retourenhaut-bouton {
    position: fixed;
    right: 30px;
    bottom: 90px;
    z-index: 1030;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 42px;
    height: 42px;
    padding: 0;
    border: 0;
    border-radius: 50%;
    background-color: #2b4c40;
    color: #ffffff;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}
#retourenhaut-bouton.retourenhaut-visible {
    opacity: 1;
    visibility: visible;
}
#retourenhaut-bouton svg {
    display: block;
    width: 20px;
    height: 20px;
}