As you can see, any two pixel wall will absorb electrons, even though the pixels themselves are not conductive. I suppose this is not indended, since it makes it very hard to predict the behaviour of electrons.
I'm not totally sure about this myself, at least with photons you get certain 'dead angles' where calculating the end result angle of a moving photon would take more time than would be convenient, causing death of the particle.
...I don't have any idea if particles like electrons and neutrons use this code though.