Very nice. The section "A word about math" really is important. I am admittedly not good at math, but I was able to build a VERY (extremely, even) rudimentary physics simulation many years ago by really really simplifying the math concepts. I was essentially iterating on the building blocks, points, lines, etc. With a lot of small steps and a lot of visual debugging lines, it ended up extremely janky and slow, but it did kinda work!
