---
title: "Shape packing puzzles: API"
package: "@phaser-ae/shape-packing"
tier: Pro
version: 3.0.0-2
released: 2026-10-14
updated: 2026-10-19
description: "The rules of fill-the-silhouette puzzles, where rotated and mirrored pieces must cover a shape exactly, on square cells, hex cells or tangram polygons."
url: https://phaser.io/packs/shape-packing/api
site: Phaser - https://phaser.io
---

# Shape packing puzzles: API

`@phaser-ae/shape-packing` — Fill a silhouette exactly with rotated, mirrored pieces on square cells, hex cells or tangram polygons, with seeded puzzles, hints and undo.

## The pack

### `shapePacking`

```ts
function shapePacking(): Pack<{ shapePacking: typeof kit }>
```

Install pure rules; no renderer, DOM or simulation hook is required.

## Helpers

### `cellAt`

```ts
function cellAt(mode: PackingConfig['mode'], point: Cell, step = 0.5): Cell
```

The board cell under a point in board units, for turning a pointer into a placement: the grid square containing it,
the nearest hex cell (by cube rounding), or in polygon mode the point snapped to multiples of `step` (default 0.5,
the lattice generated tangrams use). Throws on a non-finite point or a `step` that is not positive.

### `cellCentre`

```ts
function cellCentre(mode: PackingConfig['mode'], cell: Cell): Cell
```

The centre of a board cell in board units: grid cells are unit squares (centre x + 0.5, y + 0.5), hex cells use `hexCentre`, and polygon mode's points are themselves.

### `createShapePacking`

```ts
function createShapePacking(config: PackingConfig, certificate?: Placement[]): ShapePacking
```

Create a packing puzzle. Pieces may touch along edges; any overlap of area is refused. Throws on a bad mode, 0 or more than 32 pieces, duplicate ids, invalid cells or polygons (self-intersecting, repeated vertices, under 3 or over 64 corners), a rotation the mode does not allow, an invalid candidate, or a `certificate` that does not fill the target.

### `generateShapePacking`

```ts
function generateShapePacking(options: PackingGenerationOptions = {}): PackingGeneration
```

Cut a seeded silhouette into connected pieces and return them with a replay-checked exact cover; it makes no uniqueness claim. Throws on out-of-range options, a layout the mode does not have, or a cut into more than the 32 pieces a puzzle may have.

### `hexCentre`

```ts
function hexCentre(cell: Cell): Cell
```

The centre of hex cell (q, r) in board units, the distance between neighbouring centres being 1: pointy-top hexes, q across and r down-right, so `{ x: q + r / 2, y: r * sqrt(3) / 2 }`. Scale and offset it to draw.

## Classes

### `ShapePacking`

```ts
class ShapePacking
```

A packing puzzle's rules: square, hex or polygon pieces placed into a silhouette, with undo, redo and a solver. Get one from `createShapePacking`.

- `constructor(config: PackingConfig, private certificate?: Placement[])`
- `solveBest(maxStates = 20000): ReturnType<ShapePacking['solve']>` — A winning continuation, without changing anything: the certificate's remaining placements when they still fit around the pieces already placed, otherwise `solve(maxStates)`. Its first placement is the hint.
- `get state(): PackingState` — A copy of the state: the placements and the move count.
- `get target(): Cell[]` — A copy of the silhouette to fill.
- `get pieces(): PackingPiece[]` — A copy of the pieces.
- `points(p: Placement): Cell[]` — The cells (grid, hex) or vertices (polygon) a placement covers on the board: the piece is mirrored (if asked), rotated, moved so its smallest x and y are 0, then moved by `x`, `y`. Empty for an unknown piece.
- `preview(p: Placement): ActionResult<PackingEvent>` — Check a placement without making it. The result is valid, or invalid with a reason: `unknown-piece`, `invalid-transform`, `off-grid`, `outside-target` or `overlap`.
- `place(p: Placement): ActionResult<PackingEvent>` — Place a piece, or move it if it is already placed, as one move in the history. Returns `{ valid: true, events }`, or `{ valid: false, reason, events: [] }` for the reasons `preview` gives.
- `remove(id: string): ActionResult<PackingEvent>` — Take a piece off the board as one move in the history. An id that is not placed is invalid with the reason `not-placed`.
- `get unfilled(): Cell[]` — The target cells no piece covers yet; always empty in polygon mode.
- `get remainingArea(): number` — Target area still uncovered: a count of cells, or an area in polygon mode.
- `get solved(): boolean` — Whether every piece is placed and together they cover the target exactly.
- `solve(maxStates = 20000): SearchResult<Placement> | { status: 'unsupported'; actions: []; visited: 0 }` — Find placements for the pieces not yet placed that cover the rest of the target, by breadth-first search over at most `maxStates` positions (default 20,000), placing pieces in config order; changes nothing. Grid and hex modes try every pose at every target cell; polygon mode searches only the config's `candidates` and reports `unsupported` without them. `unsolvable` is a proof only over those placements; `budget-exhausted` is no claim.
- `undo(): boolean` — Undo the last move. Returns false when there is nothing to undo.
- `redo(): boolean` — Redo the move last undone. Returns false when there is nothing to redo.
- `reset(): void` — Return to the empty table and clear the history.

## Types

### `PackingConfig`

```ts
interface PackingConfig
```

A puzzle: the silhouette to fill, the pieces to fill it with and the moves allowed.

- `mode: 'grid' | 'hex' | 'polygon'` — The kind of board: square cells, hex cells (axial q/r) or continuous polygons.
- `target: Cell[]` — The silhouette to fill: its cells (grid, hex) or the vertices of a simple polygon (3 to 64 corners).
- `pieces: PackingPiece[]` — The pieces, 1 to 32, with unique ids.
- `rotations?: number[]` — Rotations allowed, in degrees; default 0, 90, 180 and 270 (hex: every 60). Grid needs multiples of 90 and hex of 60; polygons take any finite angle. Must not be empty.
- `reflect?: boolean` — Whether pieces may be mirrored; default false.
- `candidates?: Placement[]` — Placements `solve` searches among instead of generating them; polygon mode needs these to be solved at all. Each must be valid on an empty table.

### `PackingEvent`

```ts
type PackingEvent ={ type: 'placed'; placement: Placement } | { type: 'removed'; id: string }
```

What a successful move reports: a piece `placed` (with its placement) or `removed` (by id).

### `PackingGeneration`

```ts
interface PackingGeneration
```

A generated puzzle: the configuration, a winning set of placements and what was measured.

- `config: PackingConfig` — The puzzle, ready for `createShapePacking`; pieces are shuffled and shown in a random pose.
- `solution: Placement[]` — One placement per piece that fills the target exactly; replayed before it is returned.
- `seed: number` — The seed asked for.
- `metrics: { /** Pieces. */ pieces: number; /** Target cells, or the target's area in polygon mode. */ area: number; /** Poses each piece can take: rotations, times 2 with reflection. */ orientations: number; /** Pieces with distinct stored shapes. */ uniqueShapes: number; }` — The puzzle's structure; not a uniqueness or human-difficulty claim.

### `PackingGenerationOptions`

```ts
interface PackingGenerationOptions
```

Options for `generateShapePacking`; every field may be left out.

- `mode?: PackingConfig['mode']` — The kind of board; default `hex`.
- `difficulty?: 'easy' | 'medium' | 'hard' | 'very-hard'` — Sets the default size, piece size and reflection; default `medium`. Anything else throws.
- `seed?: number` — Seed of the random stream, an unsigned 32-bit whole number; default 1.
- `layout?: string` — The silhouette: grid `rectangle` (default), `cross` or `steps`; hex `hexagon` (default), `diamond` or `triangle`; polygon `square` (default) or `diamond`. Ignored when `target` is given.
- `size?: number` — Side (grid) or radius (hex) of the layout in cells: 2 to 12 for grid (default 4, 5, 6, 7 by difficulty) and 1 to 6 for hex (default 2, 2, 3, 3). Polygon ignores it.
- `target?: Cell[]` — Grid and hex: your own silhouette, as unique whole-number cells (hex: axial q/r), instead of `layout` and `size`. A part with fewer cells than `minPieceSize` becomes a smaller piece.
- `pieceSize?: number` — Cells a piece grows to, 1 to 12; default 5, 5, 4 and 4 by difficulty. Pieces alternate between this and one less, and merging leftovers can make one larger. Polygon ignores it.
- `minPieceSize?: number` — Fewest cells in a piece, 1 to `pieceSize`: smaller leftovers merge into a neighbour. Default 3 (or `pieceSize`, if smaller). Polygon ignores it.
- `rotate?: boolean` — False fixes every piece's orientation (the only rotation is 0); default true.
- `reflect?: boolean` — Whether pieces may be mirrored; default true from `hard` up.

### `PackingPiece`

```ts
interface PackingPiece
```

A piece of the puzzle, described in its own local coordinates.

- `id: string` — Unique id, non-empty; placements refer to it.
- `cells?: Cell[]` — Grid and hex modes: the cells the piece covers, in whole-number coordinates (hex: axial q/r).
- `polygon?: Cell[]` — Polygon mode: the vertices of a simple polygon with 3 to 64 corners and no holes.

### `PackingState`

```ts
interface PackingState
```

The puzzle's state, plain data.

- `placements: Placement[]` — The pieces now placed, at most one each, in the order they were placed.
- `moves: number` — Moves made so far, counting each placement and removal.

### `Placement`

```ts
interface Placement
```

How a piece lies on the target.

- `id: string` — Id of the piece placed.
- `x: number` — Position across of the transformed piece's minimum-x corner: a whole number of cells in grid and hex modes.
- `y: number` — Position down of the transformed piece's minimum-y corner: a whole number of cells in grid and hex modes.
- `rotation?: number` — Rotation in degrees; default 0. It must be one of the configuration's `rotations`.
- `mirrored?: boolean` — Whether the piece is reflected before it is rotated; default false. It needs the configuration's `reflect`.

### `ShapePackingApi`

```ts
type ShapePackingApi = typeof kit
```

Public headless shape packing puzzles helpers.

---

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