#actionbutton {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background-color: #bbb;
    color: #fff;
    font-size: 1.75rem; /* 28px */
    line-height: 56px;
    text-align: center;
    cursor: pointer;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
    z-index: 9999;
    transition: background 0.2s ease;
    position: fixed;
}

#actionbutton:hover {
    background-color: #ccc;
}

#actionbutton.topleft {
    top: 200px;
    left: 30px;
}

#actionbutton.topright {
    top: 200px;
    right: 30px;
}
#actionbutton.bottomleft  { bottom: 30px; left: 30px; }
#actionbutton.bottomright { bottom: 30px; right: 30px; }
#actionbutton.centre {
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}