Draggable mask

[americomiyasiro]

Hi!
I'm trying to use the touch-punch in a project for desktop and mobile. I changed the sample code you provide but I have an issue: I'm trying to make the draggable item as a mask. On the desktop it works when I edit the CSS using a background image fixed. But when I'm on mobile, the background moves with the draggable item, ignoring the css:
#draggable {
position: absolute;
top: 40px;
left: 250px;
width: 250px;
height: 250px;
border: 1px #333 solid;
border-radius: 125px;
color: #fff;
font-size: 12px;
font-family: sans-serif;
background-image:url(images/capa-livro-geografia-daltonico.jpg);
background-size: auto;
background-attachment: fixed;
background-repeat: no-repeat;
background-position: center;
}
Is there any css tip that I can't see or the touch-punch cannot be used as a mask?

Thanks!