#myBtn {
    display: none; 
    position: fixed; 
    bottom: 40px; 
    right: 30px; 
    z-index: 99; 
    border: 4px solid #15819b;
    outline: none; 
    background-color: white; 
    color: #15819b; 
    cursor: pointer; 
    padding: 15px; 
    border-radius: 50%; 
    font-size: 1.8rem; 
    font-weight: 600;
}

#myBtn:hover {
    background-color: #15819b; 
    color: white;
    font-size: 1.8rem; 
    font-weight: 600;
}