Comment by dragonwriter

I’ve only done a few toy projects using ECS, but the author seems to be struggling with ECS on a basic conceptual level. E.g.,

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For example, modelling Health as a general purpose mechanism might be useful in a simple simulation, but in every game I end up wanting very different logic for player health and enemy health. I also often end up wanting different logic for different types of non-player entities, e.g. wall health and mob health. If anything I've found that trying to generalize this as "one health" leads to unclear code full of if player { ... } else if wall { ... } inside my health system, instead of having those just be part of the big fat player or wall systems.

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The solution here is to have a Health component but not a generic Health system (actually, a generic Health system sounds like a code smell for another reason, because systems map to actions, while components map to attributes; systems that interact with a Health component would be things like a damage or healing system) -- but if you need something to work different for player health and wall health and enemy health, you can just have three systems, which, respectively, do Query<Player, Health>, Query<Enemy, Health>, Query<Wall, Health>.