Parametric jigsaw puzzle

Already half a year ago I was looking for a jigsaw puzzle in order to replace a cardboard jigsaw puzzle which is part of a geocache I own. I found a couple of candidates here on Thingiverse, but I wasn't satisfied with their configurability.

So I sat down to put together a fully parametric OpenSCAD model. The pieces are defined through a 4D-vector where the edges are either straight (a=0), inward bound (a=-1) or outward bound (a=+1).

Also the rounding of the corners using a minkowski opera