A building's construction system is responsible for supplying building NFTs to the ecosystem. To upgrade a building's tier, buildings of the same tier are used as materials (=demand). The number of buildings is reduced by the upgrading system, and the construction system is there to supply them again. However, only building owners (who are granted a construction license per building) can build new buildings, and Lay 007 Robot and $Orb are consumed as resources to construct new buildings.