A great writeup of excellent work!

The flight simulator / magic carpet easter egg in Microsoft Excel 97 used that same shaded-colormap palette trick, plus some dithering:

https://rezmason.github.io/excel_97_egg https://rezmason.github.io/excel_97_egg/about.html

I'm impressed by your sprite pipeline and gibs animations. Your attention to detail and navigation of constraints have really paid off, I can't wait to play this sometime