DF itself already computes the prosperity of your fortress for you. This score and the sheer number of (non-enemy) dwarfs are the way you progress through the g

DF itself already computes the prosperity of your fortress for you. This score and the sheer number of (non-enemy) dwarfs are the way you progress through the game. So a reward function based on these two inputs, plus maybe something like "months since last major catastrophe" could work.