Yes, the project was completely done in Excel, using only formulas and macros to enter key commands and start the animation. Video accelerated. Do not forget that this is Excel. However, on a rather old author’s computer, the demo is updated every 2 seconds, which is not so bad.
An excel file can be downloaded from GitHub , which allows you to get an intuitive understanding of how ray tracing works. Again, this is all based on The Ray Tracer Challenge by Jamis Buck, which teaches the basics of ray tracing in a fun and engaging format.