[bjngxwtp] Tetravex cube

It would be very easy to create a tetravex puzzle on the surface of a cube. It eliminates the strategy of starting on an edge.

Or, one can go fully three dimensional, packing cubelets with six neighbors each. Perhaps electrical sensors that complain if you've done it wrong. Four dimensional?

How can we objectively define the difficulty of an edge matching puzzle?  Subjectively, we could measure people attempting to solve it.