#button {
    text-decoration: none;
    display: inline-block;
    background-color: #e47b7b;
    width: 5vh;
    height: 5vh;
    text-align: center;
    border-radius: 10vh;
    position: fixed;
    bottom: 3vh;
    right: 3vw;
    transition: background-color .3s,
        opacity .5s, visibility .5s;
    opacity: 0;
    visibility: hidden;
    z-index: 500;
    box-shadow: 0px 0px 5px 1px black;
}

#button::after {
    content: "\f077";
    font-family: FontAwesome;
    position: absolute;
    font-size: 3vh;
    right: 0.87vh;
    bottom: 0.2vh;
    line-height: 5vh;
    color: #fff;
}

#button:hover {
    cursor: pointer;
    background-color: #ffa3a3;
}

#button:active {
    background-color: #a96a6a;
}

#button.show {
    opacity: 1;
    visibility: visible;
}