webview, #overlay {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

#overlay {
    background-color: #000;
    opacity: 0.5;
    transition: opacity 250ms, z-index 250ms;
    z-index: 100;
}

#overlay::before {
    content: "\26A1";
    font-size: 48px;
    color: #fff;
    text-align: center;
    display: block;
    position: absolute;
    top: 40%;
    left: 0;
    right: 0;
}