Ah nice for noticing d!=0 is d>0. Not sure how I missed the multiplication to get rid of the vector form; I guess I was too obsessed with the x-x trick...
I added your changes to the Shadertoy version with your HN nickname. I'll integrate it to the original later.
I saw that you used `float z;` to later use `z` instead of the constant `0.`.
You can also apply that to get a zero vector: `vec3 y;` and use `y` in place of `p-p`.
It seems that leaving the obsession behind some more can save another byte.
