The other intriguing aspect was how state is modeled (or rather, maybe not explicitly modeled?). A lot of the examples show the state extracted from the DOM and temporal properties indicating what the next (or eventual) state _should be_. If we want to look at the existing state (according to the model/spec) when predicting the next state (similar to how you can use s when specifying s' in TLA+), there seems to be no direct way to do that. It should of course be possible to capture the state at an earlier time in a closure and use it in a thunk at a later point, so it should be possible to work around this but that can be a little awkward, maybe. I'm working on a project in this space (primarily geared towards backend API model-based testing) and the state of the _real_ system isn't globally inspectable unlike a web page so took a different route over there. Having said that, this is a very interesting design choice that's very intriguing (in a good way).