Impossible prison cube

This very simple part is originally designed for a simple demo on a CNC Mill to quickly cut a cube with a trapped moving part inside, with only one circular cut on each cube face. But it can also be easily 3D printed with some material supports.

Designed from memories of my mechanical engineering studies 16 years ago, where the gcode for this thing was preloaded in the classroom industrial CNC Mill.

It should be scaled to any size without any issue.