#iframe_extensions {
  position: fixed;
  top: 100%;
  left: 0;
  z-index: 1000;
  width: 100%;
  height: 100%;
  border: 0;
  margin: 0;
  padding: 0;
  transition: transform .6s ease;
  background: #f4f4f4;
}

#iframe_extensions.opening {
  transform: translateY(-100%);
}

#iframe_extensions.closing {
  transform: translateY(0);
}