body.blindmode * {
    font-size: 3rem;
    background-color: black !important;
    color: yellow !important;
}

body.blindmode a:hover {
    color: black !important;
    background-color: yellow !important; 
}

div.blindmode {
    width: 70px;
    height: 70px;
    border-radius: 10px;
    border: 5px solid yellow;
    background-color: black;
    color: yellow;
    position: fixed;
    right: 0;
    bottom: 50px;
    cursor: pointer;
    z-index: 9999;
    transition: transform .3s ease-in-out;
}

div.blindmode:hover { transform: scale( 1.2 ); }

body.blindmode div.blindmode { background-color: #fff; }