Lampshade diffuser insert (parametric)

An insert for the bottom of a circular hanging lampshade, to diffuse the glare from the bulb. This assumes there is a small lip on the inside of the lampshade, on which the insert can rest. You just lift the insert into place and it's held there by gravity.

I've generated a few sample STLs, but you probably want one to match your own lampshade, so the OpenSCAD model is fully parametric, including:
* square or round (*new in v2!*)
* diameter of the shade
* width of the lip inside the shade
* number of rings
* height of the rings
* how much the rings are angled inwards (between straight up and 45 degrees)
* number of arms (*new in v2!*)
* a few other fine-tuning options

If you want a different size, you can:
* Download the OpenSCAD model, change the parameters and generate your own STL (best option!)
* Scale one of the provided STLs on the X and Y axes, and the Z too if you want, in your slicer
* Post a comment with your needs (the list above) and I will generate a bespoke STL (probabl