Glossary

Definitions grounded in the source. For where each lives, see the linked concept and system pages.

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ECS

• Entity — a generational handle { index, generation }. Despawn bumps the generation, so a stale reference is detected, not silently reused. Carries no data itself.
• Component — plain data on an entity (Transform, Velocity, Health, Team, …); any 'static + Send + Sync + Clone type. The world is a flat table of these.
• Archetype — entities are stored columnar (SoA) grouped by their exact set of components, for cache- friendly iteration. See Engine internals.

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The world-engine verbs

• observe — read the full current state exactly, without stepping (POST /observe → RichEntityData). →
• peek — the exact probability distribution over the next step’s declared outcomes, read analytically (not sampled) from the generative model. The answer key.
• step — advance one tick deterministically, sampling from exactly the distribution peek reported (POST /step).
• fork — clone the world mid-episode and branch a counterfactual (the do-operator); POST /fork. →
• peek == step — the soundness invariant: a named test holds the two distributions byte-identical. A perfect predictor scores 0 nats.

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Data & state

• WorldStateGraph — the observable world as { tick, entity_count, entities } in canonical JSON; the structured form behind observe. →
• RichEntityData — the flattened per-entity projection observe returns over HTTP.
• state_digest — a 64-bit FNV-1a hash of the observable state over a canonical ordering. Equal digests ⇔ equal observable state — the reproducibility oracle.
• JointDistribution — the per-variable distributions peek returns (per_variable: [(name, dist)]).

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Rules

• Rule — { when, do } as pure data: a condition, an optional declared distribution, and effect bundles. No closures. →
• RuleSet — the ordered collection of rules the engine evaluates each tick; rule firing order is deterministic.
• GameAction — an effect an action can apply (Spawn, Damage, Heal, Teleport, EndGame, SetField, AddField, …; SetColor/ShowText are render-gated stubs).

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Determinism & evaluation

• determinism (within-platform) — same seed + inputs ⇒ bit-identical trajectory, within one build/platform; not a claim of identical floating-point across CPU architectures. →
• OnlineWorld — the live world + the four-verb loop + a single seeded RNG stream, in euca-online.
• regret (nats) — the prequential score: Σ −ln P̂(realized) − Σ −ln P*(realized). ≥ 0 in expectation; a perfect predictor scores 0. →