Reading through the examples I thought, hey, this looks a lot like elm! And not surprisingly, the readme had this to say:
Yup, it’s greatly inspired by the elm architecture. But contrary to elm, choo doesn’t introduce a completely new language to build web applications.
“single state: immutable single state helps reason about changes”
Yes, that would make reasoning about changes trivial.
[off-topic] I recognize those graphics! That’s Kiddopaint! \o/