here's the last draft doc that reached github:
   # for designing an interface of system simulation
   # a simple system where some property is a function of time.
   # goal 1: user has access to a state containing a number, and can
   produce
   #         another state based on a time change from the first
   #         number = constant * time
   # goal 2: model user in a way that can be simulated, to mutate
   #         the constant. the simulation can be simply a uniform
   #         distribution of chance of change.
   # goal 3: simulate a single timeline, letting the user move along it
   arbitrarily,
   #         using the user's model of behavior to predict state.
   # goal 4: simulate multiple timelines, with an interface as to whether
   to bind
   #         actions to one or spawn a new one.  be nice to have that be a
   float
   #         probability of binding.
   # note: user and sim could share the same interface for predicting
   state given environment and time
   # note: user and number could both be equal peers
   # design choices/ideas:
       # - update functions take new time, not time change.  expected to
   be more refactorable if need.