Welcome to routify.js
It supports sub-routes, each one with different fallbacks.
It works everywhere
Straight HTML files. Here is a guide to turn a simple HTML file in to a routing-aware page,
lit-element. routify.js provides two mixins which will enable routing for your main page and any other pages in no time. (routify.js has a simple lit-html guide)
(more to come)
Finally, look at routify.js' API