Class: Random

Seedable pseudo-random number generator + helpers. Uses Mulberry32 — a tiny, fast 32-bit PRNG with good statistical properties for game RNG. NOT cryptographically secure; never use for tokens / signatures. The seed/state is a plain uint32, so it's trivially serializable for replays / save-load.

Determinism: identical seeds produce identical sequences across platforms and JS engines. That's the whole point — it lets you reproduce a "lucky drop" run in QA or freeze RNG in a unit test without bringing your own seeded PRNG library.

Two ways to use:

• new Random(seed) for a private stream (encounters, drops, particle bursts per scene).
• Random.shared global instance for fire-and-forget calls — auto-seeded from performance.now() at module load. Use Random.shared.SetSeed(...) to pin it.

Constructors

Constructor

new Random(seed?): Random;

Parameters

Parameter	Type
seed	number

Returns

Random

Properties

Property	Modifier	Type	Description
shared	readonly	Random	Public global. Auto-seeded once at module load — replace seed via SetSeed for reproducible runs.

Methods

Angle()

Angle(): number;

Unit-length 2D direction vector. Returns the angle in radians — callers convert as needed via Math.cos/sin or Vector2.FromAngle.

Returns

number

---

Bool()

Bool(p?): boolean;

True with probability p in [0, 1]. Default 0.5 — coin flip.

Parameters

Parameter	Type	Default value
p	number	0.5

Returns

boolean

---

Gaussian()

Gaussian(mean?, stdDev?): number;

Approximate normal distribution via Box-Muller. mean shifts, stdDev scales. Useful for natural-feeling particle spread (size jitter, lifetime variance, etc.).

Parameters

Parameter	Type	Default value
mean	number	0
stdDev	number	1

Returns

number

---

GetState()

GetState(): number;

Returns

number

---

InRect()

InRect(
   minX, 
   minY, 
   maxX, 
   maxY, 
   out
): object;

Uniform point inside an axis-aligned rect. Writes into out.

Parameters

Parameter	Type
minX	number
minY	number
maxX	number
maxY	number
out	{ x: number; y: number; }
out.x	number
out.y	number

Returns

object

Name	Type
x	number
y	number

---

Int()

Int(min, max): number;

Uniform integer in [min, max] inclusive on both ends.

Parameters

Parameter	Type
min	number
max	number

Returns

number

---

InUnitCircle()

InUnitCircle(out): object;

Uniform point inside a unit circle. Writes into out to avoid allocation. The sqrt() is what keeps the distribution uniform — without it, points cluster near the center.

Parameters

Parameter	Type
out	{ x: number; y: number; }
out.x	number
out.y	number

Returns

object

Name	Type
x	number
y	number

---

Next()

Next(): number;

Uniform float in [0, 1). Mulberry32 — drop-in for Math.random() with a 2^32 period.

Returns

number

---

Pick()

Pick<T>(array): T | undefined;

Pick a random element from a non-empty array. Returns undefined for empty arrays.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
array	readonly T[]

Returns

T | undefined

---

Range()

Range(min, max): number;

Uniform float in [min, max).

Parameters

Parameter	Type
min	number
max	number

Returns

number

---

SetSeed()

SetSeed(seed): void;

Parameters

Parameter	Type
seed	number

Returns

void

---

SetState()

SetState(state): void;

Parameters

Parameter	Type
state	number

Returns

void

---

Shuffled()

Shuffled<T>(array): T[];

Allocating shuffle — for callers that want to keep the original order.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
array	readonly T[]

Returns

T[]

---

ShuffleInPlace()

ShuffleInPlace<T>(array): T[];

Fisher-Yates in place. Mutates and returns the input array.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
array	T[]

Returns

T[]

---

Sign()

Sign(): number;

+1 / -1 with equal probability. Convenient for flipping a direction.

Returns

number

---

WeightedIndex()

WeightedIndex(weights): number;

Pick an index from an array of weights — Pick-equivalent for non-uniform distributions. Negative weights are clamped to 0. Returns -1 if total weight is 0.

Parameters

Parameter	Type
weights	readonly number[]

Returns

number