When I had HTC the thing I remember similar to this was a cover with holes in it and the phones screen itself made the patterns. Is that what this one is like? That would explain how it doesn't require a battery. The inside of the Samsung case looks a little better than the HTC case did.
In this video I found for it you can actually see the speakers and bezels through the case and at one point he whips the case open to show that it is the display providing the images. I also didn't remember it being interactive through the case but it was. The price is probably why I never tried or thought about trying it.
https://youtu.be/d7n34bkF-Ew