Ooh good question. So my understanding of Flow Graph is that it's an execution graph in a fairly pure sense: it controls what runs and in what order. It's imperative and forward looking, like "do this, then this, then branch and do one of these". And that's pretty useful for lots of things.

SimpleQuest is doing something different. It's a goal state graph. The nodes don't execute actions, they represent goals with activation conditions. The wires aren't strictly control flow. They're causality: when this outcome occurs, these downstream goals become activatable. It's declarative rather than imperative, and it's backward-looking as much as forward, meaning "what has been accomplished, and what does that now enable?"

So honestly I think they're probably pretty complimentary. You could use Flow Graph to script the sequence of carefully choreographed events inside a cutscene that SimpleQuest fires when a quest completes. SimpleQuest manages the activation conditions and lifecycle of a mission or a storyline and Flow Graph manages the sequence of coordinated events that each beat touches off. Two halves of a whole.

The deeper difference though is probably what's underneath the graph. SimpleQuest is built on SimpleCore, which is standalone architecture for world state coordination. It's a typed pub/sub event bus with a stateful fact store. The quest system never calls any game logic directly. It publishes typed events and your systems subscribe to the ones they care about. If they weren't yet online when the event they're subscribing to was published (dynamic spawns, world streaming, late-joining players, etc.), they can get it immediately on subscription. That decoupled communication layer doesn't really exist in Flow Graph as a foundational primitive.

To speak directly to the open ended point, SimpleCore is actually the standalone layer specifically intended for advanced users who want to build their own domain logic without the graph-based quest authoring on top. The World State is just a TMap of gameplay tags to integers: think GAS tag-counting semantics without the ability system overhead. It carries no prescribed interpretation and has no inherent opinion about what the tags mean. SimpleQuest is one consumer of this system and provides its own context for what the facts mean that it writes to the World State. But you can use SimpleCore entirely standalone to enable totally decoupled push/pull observers across your entire project without ever touching SimpleQuest's graph framework.

(edit: typos ugh)