RNG

rng(seed) returns a deterministic mulberry32 generator. Seed 0 is fine.

import { rng } from "@f0rbit/forge";

const r = rng(1);
r.next();           // → number in [0, 1), uniform
r.int(0, 9);        // → integer in [0, 9] inclusive
r.pick([1, 2, 3]);  // → Result<T, EngineError>; err({ kind: "empty_array" }) on empty

const enemies = r.fork("enemies");  // independent substream
const loot    = r.fork("loot");     // independent substream

Forking

Forking mixes the parent state with a label hash to derive a child seed. Forks let you advance subsystems independently — if you reorder enemy code one day, the loot RNG stream isn’t disturbed. Use forks when you have a clearly-bounded subsystem; one root RNG is fine for small games.

State + restore for snapshot

const s = r.state();   // → number (current internal state, not the seed)
r.restore(s);          // → identical sequence resumes
r.seed;                // → original seed

Snapshot round-trips rng_state and rng_seed (see Storage / persistence).