* provide an explicit sequencing of when actors take their turns, passing updated resources to each in turn. This is your "step by step" imperative approach, and you're basically writing a main game loop. * don't sequence the actors, but implement a lock on the resource using a TVar. This is the simplest async approach. * many more approaches I haven't thought of

The point of FP is to be provide as much information about the logic of the program as possible. If two actors can move to the same point at the same time, then you need to write down logic to handle that case, whether actors move in sequence or independently.

Not writing down that logic because "I have an imperative language" is how you get bugs, especially race conditions.