Not working very well in Chrome, either. I'm not sure if I'm not supposed to be able to drag it, but my first reaction was to try, and I wound up dragging the transform'ed images around.
To prevent dragging the images, one could obviously use a div with a background-image, like this stupid demo I made: https://jsbin.com/yaqezo/
However,
.screenshots img
{
pointer-events: none;
-webkit-user-select: none;
-moz-user-select: none;
}