Rounded wall for calibration - Parametric

A rounded square wall generator. Takes only 4 values:

Size
Height
Thickness
Roundness

I designed this to create thin wall models for calibrating 3d printer nozzle flow rates. The edges are rounded off, which introduces the only limitation in the system: you must have walls at least twice as long as the rounding, if you'd like to understand better why, feel free to read the "thin wall.scad" and/or the Minkowski documentation: https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Transformations#minkowski

There are lots of good calibration guides, like this one https://www.thingiverse.com/thing:52946

Unfortunately the only thin wall model I could find caused weird print errors, an STL error perhaps.

Rather than keep hunting for a STL, I thought I'd make this generator, so anyone could make their own calibration model.