This is neat! I've gone down the SDF rabbit hole a bit, recently. I'm glad you added some links to iq's site; he's got great stuff.

I feel compelled to link to his "happy bouncing" shader, which is phenomenal IMO: https://www.shadertoy.com/view/3lsSzf

(with associated 6 hour (!) youtube video on its creation)

That's a juicy ~500 lines of code (: