When User 1 wishes to share a photo on his/her device, he/she touches the image in the photo gallery (at screen level, z=0) with a long press and thus ‘pushes’ it to the shared layer. The image appears on the shared layer of the other device, and is now seen on both Device 1 and 2 GUIs on the shared layer (below the screen level). If User 2 wishes to store the shared photo on his/her own device, a photo on a shared layer can be brought to the private layer with a long press. In addition to moving pictures
between the private and shared layer with a long press, the prototype supports enlarging a picture (with a single tap) and browsing the collection of photo thumbnails (with a swipe gesture).