Technology as Constraint
Every technology changes what is possible. Firearms end the era of armor. Cell phones end the era of the alibi. The internet ends the era of information asymmetry between individuals and institutions. When writing in any period, ask: what can characters NOT do because of the technology level? The absence of technology is as structurally important as its presence. A story set before GPS requires characters to navigate differently, to get lost, to be unreachable. A story set before antibiotics requires characters to fear infection in ways we have largely forgotten. Technology defines the possible; its absence defines the shape of constraint.