I can't be thankful enough for all this time you spent on writing and re-writing the script!
You added an extra feature - background option! Now there is nothing i can think of that could possibly make this script better.
The same effect in Inkscape is in Filters>Shadows and Glows>In and Out. It does not have animation option and I made that animation
just to get a better idea about In&Out effect. When I made a request for such a script i thought about your Plastic or Glass script
, which came out really great and I figured you'd be one of few persons up to the challenge. Turned out I was right.
Thank you again, Graechan!