This is so cool and I would have loved to have had this while I was still an academic for diagrams and interactively playing around with setups. For real design, of course the maths gets harder and the software get more expensive. The closest alternatives that I found before were optgeo[1] and OpticalRayTracer[2] but an inkscape plugin like this is much more useful for making diagrams for article, posters and presentation.

[1] http://jeanmarie.biansan.free.fr/optgeo.html [2] https://arachnoid.com/OpticalRayTracer/