#pwa-install-button {
    position: fixed;
    right: 16px;
    bottom: 16px;
    z-index: 10000;
    padding: 13px 18px;
    border: 1px solid #b00000;
    border-radius: 10px;
    background: #111;
    color: #fff;
    box-shadow: 0 8px 24px rgba(0,0,0,.45);
    font: 700 14px Arial, sans-serif;
    cursor: pointer;
}

#pwa-install-button:disabled {
    opacity: .65;
    cursor: wait;
}

@media (min-width: 821px), (display-mode: standalone) {
    #pwa-install-button {
        display: none !important;
    }
}