The machine uses gravity and a slight backward tilt of the front window assembly to sort coins using specially-sized windows cut into the cardboard. The coins want to fall backwards, so when they get to the right window, they drop off the ramp, thus ensuring that they don't fall into a larger window farther down on the ramp.
I also engraved the name "Moolah Masta 3000" and some icons into the front of the sorter using my laser cutter. I have a category of posts related to building the laser cutter and fixing the issues that sprang up with its scavenged parts.
So far, the soin sorter hasn't every mis-sorted coins or gotten them awkwardly stuck. For having no moving parts, it works surprisingly well!