[Reef]

It is a bit hard to read code with one-letter variable names

[syllogism]

I took them from the original post. I imagine they're the standard forms of the equations.

[zellyn]

I'm not sure why position is "r", but F for force, m for mass, w for world (in a short function), N for, well, N - doesn't seem too bad. Math looks much worse if you spell everything out.

[randlet]

It's pretty standard to use r as a position vector in physics.

[stefantalpalaru]

He's following the code in the original article: https://www.crumpington.com/blog/2014/10-19-high-performance...

Makes side by side comparisons easier.