---
title: "Slingshot siege: API"
package: "@phaser-ae/slingshot-siege"
tier: Pro
version: 3.0.0-1
released: 2026-10-19
updated: 2026-10-19
description: "A physics demolition game on real rigid bodies, where shots slung at wood, glass and stone structures bring them down, with seeded levels each proven winnable."
url: https://phaser.io/packs/slingshot-siege/api
site: Phaser - https://phaser.io
---

# Slingshot siege: API

`@phaser-ae/slingshot-siege` — Slingshot demolition on real rigid bodies: shots at wood, glass and stone structures that collapse, goals to destroy, levels proven winnable, as in Angry Birds.

## The pack

### `slingshotSiege`

```ts
function slingshotSiege(): Pack<{ slingshotSiege: SlingshotSiegeApi }>
```

The `slingshot-siege` pack: Angry Birds' rules on real rigid bodies, independent of rendering.

## Helpers

### `createSlingshotSiege`

```ts
const createSlingshotSiege = (config: SiegeConfig): Promise<SlingshotSiege>=> …
```

Create a round, the same as `SlingshotSiege.create`.

### `generateSiege`

```ts
async function generateSiege(o: SiegeOptions = {}): Promise<SiegeLevel>
```

Generate a level and prove it winnable by playing it through the physics. Throws on an option outside its bounds,
and when no certified arrangement is found in 30 attempts.

### `SIEGE_FAMILIES`

```ts
const SIEGE_FAMILIES: readonly SiegeFamily[]
```

Every structure family.

## Classes

### `SlingshotSiege`

```ts
class SlingshotSiege
```

A siege round on its own rigid world.

- `readonly config: SiegeConfig` — The configuration it was created with (an owned copy).
- `static async create(c: SiegeConfig): Promise<SlingshotSiege>` — Create a round with its own physics world; resolves when the rigid-body runtime is ready. Throws on an unknown material, duplicate piece ids, or a number outside its bounds.
- `get state(): SiegeState` — A fresh copy of the state, with every body's pose.
- `get solved(): boolean` — Whether the round is won.
- `get lost(): boolean` — Whether the round is lost.
- `get busy(): boolean` — Whether a shot is still settling.
- `get origin(): Point` — Where shots leave from.
- `trajectory(velocity: Point, seconds = 2): Point[]` — The free flight of a shot at `velocity` for `seconds` (0.1 to 5, default 2), as 41 points.
- `aimAt(point: Point, flight = 0.8): Point | null` — The launch velocity that lands on `point` after `flight` seconds (default 0.8), or null when that would need more than `shotSpeed`.
- `aimFromDrag(dx: number, dy: number): Point | null` — The velocity of a slingshot drag of (dx, dy): opposite the drag at 4.5 a unit, capped at `shotSpeed`, with z 0; null for a drag too short to launch. Throws when dx or dy is outside -30 to 30.
- `fire(velocity: Point): { valid: boolean; reason: string }` — Fire at `velocity`. Invalid, firing nothing, when the round is over, the shots are spent, a shot was fired in the last 0.2 s or one is still settling. Throws when the velocity is out of bounds.
- `step(dt: number): void` — Advance by `dt` seconds (0 to 0.1) in fixed 1/120 s ticks; the remainder carries to the next call.
- `hint(): { target: string; velocity: Point } | null` — A shot at a standing goal, leftmost first: its id and a velocity that reaches it, or null.
- `reset(): void` — Rebuild the round: every piece whole, the shots restored, the history cleared.
- `undo(): boolean` — Take back the last shot by rebuilding the world and replaying the earlier ones; false if there is none.
- `redo(): boolean` — Replay a shot `undo` took back; false if there is none.
- `dispose(): void` — Release the physics world; the round cannot be used afterwards.

## Types

### `SiegeConfig`

```ts
interface SiegeConfig
```

A siege round: the structure, the launcher and the limits.

- `pieces: LaunchPiece[]` — Every piece, from 1 to 160, with distinct ids.
- `origin: Point` — Where shots leave from, world units.
- `gravity: number` — Gravity along y in world units a second squared, from -30 to 0 (negative pulls down).
- `ammo: number` — Shots at the start of the round, a whole number from 1 to 80.
- `shotSpeed: number` — The fastest a shot may leave, world units a second, from 5 to 40.
- `materials?: Record<string, MaterialDef>` — Materials by name, merged over `DEFAULT_MATERIALS`.
- `goals?: string[]` — The materials whose pieces must all be destroyed to win. Default `['goal']`.
- `floor?: { x: number; y: number; z: number; sx: number; sy: number; sz: number } | null` — The ground the structure stands on: a static box (centre and full size). Default 70 by 1 by 12 at (3, -0.5, 0); null for none.
- `settle?: number` — Seconds a shot may take to settle before the next may be fired. Default 6.

### `SiegeFamily`

```ts
type SiegeFamily = 'towers' | 'bridges' | 'pyramid' | 'staircase' | 'fortress' | 'cantilever'
```

The structure families: posts and roofs in towers, spans on piers, brick pyramids, stone stairs with a goal on each
step, stone fortresses with glass roofs, and a weighted cantilever.

### `SiegeLevel`

```ts
interface SiegeLevel
```

A generated level and the proof that it can be won.

- `seed: number` — The seed it was generated from.
- `difficulty: Difficulty` — The difficulty it was generated at.
- `config: SiegeConfig` — The round to play: pass it to `createSlingshotSiege`.
- `parameters: Required<SiegeOptions>` — The options with every default filled in; pass them back to get the same level.
- `solution: { time: number; velocity: Point }[]` — A winning sequence the generator played through the physics: each shot's velocity and when it was fired.
- `metrics: { family: string; encounters: string[]; groups: number; pieces: number; targets: number; certificateShots: number; duration: number; structure: string }` — The level's structure family and encounters, counts, the verified shot count and its duration.

### `SiegeOptions`

```ts
interface SiegeOptions
```

Options for `generateSiege`; each is optional and checked against its bounds.

- `seed?: number` — Unsigned 32-bit seed. Default 1.
- `difficulty?: Difficulty` — `easy`, `medium`, `hard` or `very-hard`. Default `medium`.
- `groups?: number` — Assemblies, from 1 to 8. Default 2, 3, 4 or 5 by difficulty, plus 1 on an odd seed.
- `pattern?: 'auto' | SiegeFamily` — The structure family the level opens with (the seed picks one for `auto`); others are mixed in after it.
- `ammo?: number` — Shots at the start, from 1 to 60. Default 3 a group plus 3, 2, 1 or 0 by difficulty.

### `SiegeState`

```ts
interface SiegeState
```

The round's state, an owned copy.

- `time: number` — Seconds simulated since the round started or was reset.
- `ammo: number` — Shots left.
- `shots: number` — Shots fired.
- `score: number` — Points: each destroyed piece's material score.
- `destroyed: string[]` — Ids of the pieces destroyed, in order (pieces knocked out of the play area count).
- `busy: boolean` — Whether a shot is still settling; no shot can be fired meanwhile.
- `lost: boolean` — Out of shots with a goal standing.
- `solved: boolean` — Every goal destroyed, once settled.
- `stars: number` — Rating from 1 to 3 once solved, 0 before: three for using at most six tenths of the shots, two for fewer than all, one otherwise.
- `poses: LaunchPose[]` — Every body's pose, for the renderer.

### `SlingshotSiegeApi`

```ts
type SlingshotSiegeApi = typeof kit & { DEFAULT_MATERIALS: typeof DEFAULT_MATERIALS }
```

`game.slingshotSiege`: the round, its generator and the built-in materials.

---

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