Heuristic presented in the talk: to verify whether a set of events belongs to one module, ask 'what happens after this event?' and 'what happens before this event?'. Multiple possible answers (e.g. creature-added-to-army can follow creature-recruited, creatures-surrendered, or combat-finished) signal a module boundary and the need for a thick line plus an Automation between them. Running these experiments on a whiteboard saves hours of coding and refactoring versus discovering the coupling at implementation time.