Same. I've been using Bevy to experiment with some accessible game mechanics for the past few months now. The speed from which I can go from "I really want map exploration to report this and that detail on an entity, based on this and that characteristic," to code that just works and does what I want, is astounding. The degree to which I can then optimize that code, to only run it when this or that component changes value for instance, is also amazing. And when some Bevy subsystem or other isn't up to my standards, I can plug in some other library, add a few components in my game, and more or less forget about the details of the lower-level integration. It's an amazingly productive engine. If it'd launched a year earlier, I'd probably have built my just released game in Bevy rather than Godot.

The way that you can turn normal Rust functions into systems, grabbing the relevant components through their type signature is wonderful sugar, and feels magic to use.

That's the level of Rust I wish there were more learning materials about.

I tried to make sense of the tutorial with various degrees of success :) Does this mean the components get automatically iterated over in no particular order (for instance the Persons in the example)?

That's correct.

Have you ever used an ECS system? This isn’t unique.

I don't know if it's unique, but it is the first ECS I've used where the level of sugar matches my mental model of what's going on behind the scenes.

I've primarily used specs & Unity's ECS before this.

The ergonomics are certainly top notch. The only other ECS I've used is the in-progress Unity one, and boy is that _painful_ by comparison.

Leveraging the type system with a good focus on generics as a means to achieve an ergonomic API may not be unique but well executed.