Entity-component-system paradigm. Compared to OOP, ECS is more "data-first". It's like a database of components (attributes such as Position, Velocity, Player) with entities (simple integer identifiers) as keys. Systems are functions that query for components and perform actions on them. See Shipyard, enTT, Bevy, flecs, etc. The design space is still evolving.

As a database guy I really can get around this. OOP hurts my head sometimes when the hierarchies get too deep.