#myBtn {
    display: none;
    position: fixed;
    bottom: 5px;
    right: 25px;
    z-index: 99;
    font-size: 12px;
    border: none;
    outline: none;
    background-color:  #1fb249;
    color: white;
    cursor: pointer;
    padding: 15px;
    border-radius: 20px; /* was 4px */
    width: 80px;
}

#myBtn:hover {
    background-color:  #1fb249;
}