this is a small library I enjoyed writing in Rust in the past few months, hope you enjoy the read
Is this essentially an alternative to an ECS?
It's a bit different, but there are analogies.
ECS gives you more control over the components of your entities, it let's you query them filtering by their specific components, and it's more efficient due to how objects are layed out in memory.
This library on the other hand, also takes care of how your entities are going to be stored in memory, but it also provides a runtime that let's you move forward generation after generation (that you could see as the main System), and it focuses specifically on let you describing the behavior of your entities more than providing mechanisms to query them (even though one of the strongest features is the ability to query surrounding entities according to your own logic).