@Phil see
https://gist.github.com/michaelsbradleyjr/b473c6099399eec5fdcedf016fe30b5a

> Key ideas:
>  Rx consumer does not control rate of reaction (producer does) so
>   consumer's effect order exhibits non-deterministism
>  Ix consumer does control rate of reaction so consumer's effect order is
>   totally determined by the consumer

I'm running it with `node rix.js` in a temp dir after `npm i ...` in that dir,
no need for package.json ceremony, etc.