Production is a RECIPE economy: input material → output material conversion. Buildings have no LEVELS; increasing capacity = MORE buildings of the same factory.
Example: a Furniture Factory needs 3 Wood + 1 Textile → produces 4 Furniture. If there's no wood, the alternative recipe (plastic) kicks in. On a building's page, every material in the recipe is clickable.
STORAGE: every material has a target (default 90 days); the excess is exported. If storage fills up and it cannot be exported, production is throttled (resources aren't wasted).
Factories cost maintenance and wages; their profit is recipe output minus inputs minus operating cost.