a bit more info about what this is & how to use it

glsl/raymarching.js

// # Rendering Signed Distance Functions with WebGL
//
// Yes, you can do this in Shadertoy, but this is how you can do it from scratch.
// (It also loads a lot faster.)
//
// Use it by opening the Scratchpad in Firefox and evaluate the code with `Ctrl-R`
// to rerender.  Including via `<script>` should also work.
//
// # Resources
//
// - [Raw WebGL](http://nickdesaulniers.github.io/RawWebGL) ([video](https://www.youtube.com/watch?v=H4c8t6myAWU))