No new pixels today, because implementing transparency and refraction turned out to be quite a lot of work. So far I’ve made all the cases where nothing happens, and the refracted ray would be black.

Fitting that the halfway point would be about reflections. Pagewise we’re more than halvway through the book, but I’m guessing that there will be plenty of things to do for the remaining 15 days. There’s still the going back and replacing the homebuilt algebra code with stdlib, if nothing else.