> For the complete documentation index, see [llms.txt](https://wise-shepherd-games.gitbook.io/theia-ecs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wise-shepherd-games.gitbook.io/theia-ecs/world-level-state.md).

# World-Level State

State that belongs to the world

Not all state in a simulation belongs to an entity, **world-wide concerns that don't map naturally onto the entity-component mode**l: world temperature, the current season, total iron mined, active threat level. Theia provides two mechanisms for this:

* **Uniques**: a **single world-wide mutable instance of a blittable component** type;
* **Resources:** **an immutable, *****enum-keyed***** store for managed reference-type data**. Use for assets and data that components need to reference but cannot hold directly due to the blittable constraint.

Both live on the world and are accessible from any system or query callback.