Nice. The fact that we can get lenses with built in shutters and film holders with built in dark slides means that we can get great results with the most simple of cameras, as your foam core example shows. All we really need is a box to keep the darkness in with a lens at one end and the film holder at the other.

This makes it easy for any of us to make a camera and is doesn't matter if we are master craftsmen or bodgers with gaffer tape!