---
title: "Flexible dice: API"
package: "@phaser-ae/dice-core"
tier: Free
version: 3.0.0-2
released: 2026-10-14
updated: 2026-10-19
description: "Dice of any kind for any game, numeric or symbolic, weighted, mixed in one pool and held between rolls, with reproducible rolls, saves and exact probabilities."
url: https://phaser.io/packs/dice-core/api
site: Phaser - https://phaser.io
---

# Flexible dice: API

`@phaser-ae/dice-core` — Arbitrary numeric or symbolic weighted dice, mixed pools, holds, reproducible rolls and bounded exact probability utilities.

## The pack

### `diceCore`

```ts
function diceCore(): Pack<{ diceCore: typeof rules }>
```

Install generic dice, holds, reproducible randomness and finite probability utilities.

## Helpers

### `createDicePool`

```ts
function createDicePool(options: DiceOptions): DicePool
```

Construct an independently usable dice pool.

### `diceProbability`

```ts
function diceProbability(dice: readonly DieDefinition[], predicate: (values: readonly (number | string)[]) => boolean, budget = 100000): ProbabilityResult
```

Exact probability for any numeric/symbolic predicate on independent dice, bounded before enumeration.

### `diceSumDistribution`

```ts
function diceSumDistribution(dice: readonly DieDefinition[], budget = 100000): { status: 'exact'; sums: { value: number; probability: number }[]; operations: number } | { status: 'budget-exhausted'; operations: number; budget: number }
```

Convolve integer-valued dice sums; supports negative/custom/weighted values and reports work exhaustion.

### `standardDie`

```ts
function standardDie(id: string, sides = 6, start = 1): DieDefinition
```

Create a fair numeric die, including d4/d6/d8/d10/d12/d20 or other finite sizes.

## Classes

### `DicePool`

```ts
class DicePool
```

A headless mixed dice pool. Rules about turns, reroll limits and scoring belong to consumers.

- `constructor(options: DiceOptions)`
- `observation(): { dice: { id: string; face: DieFace | null; held: boolean }[]; rolls: number }` — Copies of currently showing faces; no random state or future outcomes.
- `hold(id: string, held: boolean): DiceResult` — Set a hold only on a die that has been rolled. Rejections do not consume randomness.
- `release(): void` — Release all holds; useful at a game-defined turn boundary.
- `apply(action: DiceAction): DiceResult` — Apply a generic command; consumers may record these for deterministic animated replay.
- `roll(ids?: readonly string[]): DiceResult` — Roll unheld dice, or an explicit subset of unheld IDs. Selection is validated atomically.
- `snapshot(): DiceSnapshot` — Save data contains RNG state and must not be passed to a bot/hint as an observation.
- `restore(snapshot: DiceSnapshot): void` — Restore validated state for this exact pool; failure leaves the live pool unchanged.

## Types

### `DiceAction`

```ts
type DiceAction = { kind: 'roll'; ids?: string[] } | { kind: 'hold'; id: string; held: boolean } | { kind: 'release' }
```

Generic replayable commands; no game-specific roll or score limits.

### `DiceEvent`

```ts
type DiceEvent = { kind: 'roll'; roll: number; dice: { id: string; face: DieFace }[] } | { kind: 'hold'; id: string; held: boolean }
```

One ordered, public dice event.

### `DiceOptions`

```ts
interface DiceOptions
```

Configuration for a renderer-independent dice pool.

- `seed: number` — Unsigned 32-bit seed.
- `dice: DieDefinition[]` — One to 64 independently rolled dice.

### `DiceResult`

```ts
type DiceResult = { ok: true; events: DiceEvent[] } | { ok: false; reason: string }
```

Accepted action and its events, or a rejection with no mutation.

### `DiceSnapshot`

```ts
interface DiceSnapshot
```

A serializable dice pool with restorable random state.

- `version: 1` — Snapshot format.
- `options: DiceOptions` — Original definitions and seed.
- `randomState: number[]` — Where the kernel's seeded stream stands (the four words of `createRng(seed).snapshot()`). The pool draws from this array in place, so a copy of the snapshot is a copy of the stream. Privileged save data, not a future-roll hint.
- `faces: (string | null)[]` — Face IDs, null before the first roll.
- `held: boolean[]` — Held dice are excluded from ordinary rolls.
- `rolls: number` — Number of successful rolls.

### `DieDefinition`

```ts
interface DieDefinition
```

An arbitrary finite die. Multiple dice may use the same faces.

- `id: string` — Unique within the pool.
- `faces: DieFace[]` — One to 256 distinct faces.

### `DieFace`

```ts
interface DieFace
```

A numeric or symbolic face; its stable ID is independent of its display label.

- `id: string` — Unique within this die.
- `value: number | string` — Game-defined numeric or symbolic result.
- `label?: string` — Optional display text.
- `weight?: number` — Positive relative probability; default 1.

### `ProbabilityResult`

```ts
type ProbabilityResult = { status: 'exact'; probability: number; outcomes: number } | { status: 'budget-exhausted'; required: number; budget: number }
```

Exact finite enumeration succeeds only when the complete support fits the budget.

---

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