---
title: "Boarding queue puzzles: API"
package: "@phaser-ae/boarding-queue"
tier: Pro
version: 3.0.0-3
released: 2026-10-14
updated: 2026-10-19
description: "The rules of bus-boarding colour puzzles, where passengers board matching buses through a few waiting spaces or loading bays, with seeded levels, undo and hints."
url: https://phaser.io/packs/boarding-queue/api
site: Phaser - https://phaser.io
---

# Boarding queue puzzles: API

`@phaser-ae/boarding-queue` — Board coloured passengers onto matching buses through limited waiting spaces or loading bays, with seeded levels, as in Bus Jam and Bus Out.

## The pack

### `boardingQueue`

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

Compose the boarding-queue public rules and generator helpers.

## Helpers

### `createBoardingQueue`

```ts
const createBoardingQueue = (config: BoardingConfig, solution?: BoardingAction[])=> …
```

Create a boarding puzzle. Throws on a configuration it refuses (out-of-range sizes, overlapping passengers, seats per colour that do not match passengers) or a `solution` that does not replay to a win.

### `generateBoardingQueue`

```ts
function generateBoardingQueue(options: BoardingGenerateOptions): BoardingLevel
```

Generate a level whose solution is replayed before it is returned. Throws on out-of-range options, a crowd that does not fit its board (`generation: requested groups exceed layout capacity`) or a lot the traffic generator cannot build.

## Classes

### `BoardingQueue`

```ts
class BoardingQueue
```

A boarding puzzle's rules, with undo, redo and a bounded solver. Get one from `createBoardingQueue`.

- `constructor(config: BoardingConfig, solution: BoardingAction[] = [])`
- `get config(): BoardingConfig` — A copy of the configuration.
- `get state(): BoardingState` — A copy of the current state.
- `get solved(): boolean` — True when every bus has filled up and left.
- `get lost(): boolean` — True when the puzzle is unfinished and no move is legal (see `deadlock()` for why). A position can be hopeless before this turns true; only `solve` can tell.
- `activeVehicle(): BoardingVehicle | null` — Passenger mode: the bus now loading (a copy), or null once all have left or in vehicle mode.
- `accessible(): { id: string; path: Cell[]; }[]` — Passenger mode: the passengers who can walk out now, each with its path from an entrance to the passenger (empty cells only).
- `dispatchRoutes(id: string): string[]` — Vehicle mode: the ids of the routes bus `id` can drive out by now (whole route clear); empty in passenger mode.
- `preview(a: BoardingAction): ActionResult<BoardingEvent>` — What `apply` would return for `a`, without playing it.
- `apply(a: BoardingAction): ActionResult<BoardingEvent>` — Play a move. Returns `{ valid: true, events }`, or `{ valid: false, reason, events: [] }` and changes nothing; reasons include `inaccessible-passenger`, `waiting-full`, `bays-full`, `wrong-mode`, `unknown-item`, `already-complete` and the traffic pack's route reasons (`blocked`).
- `legalActions(): BoardingAction[]` — Every legal move now, those that serve the wanted colour first.
- `deadlock(): BoardingDeadlock` — Why the player is stuck, or `deadlocked: false`.
- `solve(maxStates = 20000): SearchResult<BoardingAction>` — A winning continuation from here, without changing anything: the rest of the creation certificate when it still applies, otherwise a depth-first search of at most `maxStates` positions (default 20,000). `unsolvable` is a proof; `budget-exhausted` is not.
- `undo(): boolean` — Take back the last move; false when there is none.
- `redo(): boolean` — Replay the move last taken back; false when there is none.
- `reset(): void` — Return to the start and clear the undo and redo history.

## Types

### `BoardingAction`

```ts
type BoardingAction = { type: 'passenger'; id: string; } | { type: 'dispatch'; id: string; route: string; }
```

A move: walk a passenger out (passenger mode), or drive bus `id` out by its route `route` (vehicle mode).

### `BoardingConfig`

```ts
type BoardingConfig = PassengerBoardingConfig | VehicleBoardingConfig
```

A boarding puzzle: Bus Jam (`mode: 'passengers'`) or Bus Out (`mode: 'vehicles'`).

### `BoardingDeadlock`

```ts
interface BoardingDeadlock
```

Why the player is stuck, from `deadlock()`.

- `deadlocked: boolean` — True when the puzzle is unfinished and no move is legal.
- `reason: 'none' | 'waiting-full' | 'bays-full' | 'inaccessible-queue' | 'no-matching-vehicle'` — `waiting-full` (every waiting space holds the wrong colour), `inaccessible-queue` (the needed passengers are walled in), `bays-full` (every bay holds a bus whose colour is not at the front), `no-matching-vehicle` (no bus of the front colour can get out), or `none`.
- `neededKey: string | null` — The colour wanted now: the loading bus's (passenger mode) or the front passenger's (vehicle mode); null when none is.
- `waiting: string[]` — Ids of the passengers in the waiting spaces.
- `bays: string[]` — Ids of the buses in the loading bays.
- `blocked: string[]` — Ids that cannot move now: passengers with no free path to an entrance, or buses with no clear exit route.

### `BoardingDifficulty`

```ts
type BoardingDifficulty = 'easy' | 'medium' | 'hard' | 'very-hard'
```

Generator tier: bigger crowds, more colours, fewer waiting spaces and more interleaving as it rises.

### `BoardingEvent`

```ts
type BoardingEvent = { type: 'waiting' | 'boarded'; id: string; vehicle: string; } | { type: 'departed'; id: string; } | { type: 'dispatched'; id: string; route: string; }
```

What a move did, in order: a passenger took a waiting space (`waiting`) or a seat (`boarded`; in vehicle mode its id is `line-<index>`), a bus was dispatched to a bay (`dispatched`) or filled up and left (`departed`).

### `BoardingGenerateOptions`

```ts
interface BoardingGenerateOptions
```

What `generateBoardingQueue` takes; everything but `seed` defaults from `difficulty`.

- `seed: number` — Unsigned 32-bit seed (0 included); the same options give the same level.
- `mode?: 'passengers' | 'vehicles'` — `'passengers'` (Bus Jam, the default) or `'vehicles'` (Bus Out).
- `difficulty?: BoardingDifficulty` — Tier that sets the other defaults; default `'medium'`.
- `layout?: BoardingLayout` — Passenger mode: the floor plan; default `'rectangle'`. Ignored in vehicle mode.
- `groups?: number` — Passenger mode: how many buses, 2 to 32; default 4, 8, 12 or 18 by tier. Vehicle mode takes its fleet from `traffic`.
- `colors?: number` — Distinct colours, 2 to 8; default 3, 4, 6 or 8 by tier.
- `seats?: number` — Seats on every bus, 2 to 8; default 3.
- `waitingCapacity?: number` — Waiting spaces (passenger mode) or loading bays (vehicle mode), 1 to 12; default 7, 5, 3 or 2 by tier.
- `lookahead?: number` — How many later buses' passengers are mixed into each bus's turn, 0 to the smaller of `waitingCapacity` and `colors - 1` (vehicle mode: below `waitingCapacity`); default 0, 1, 2, 2 (vehicles 0, 1, 2, 1) by tier. Higher means more of the waiting space is needed.
- `traffic?: Omit<TrafficGenerateOptions, 'seed'>` — Vehicle mode: options for the bus lot, passed to `generateTrafficRelease`; default the `parking` preset at size 4, 6, 8 or 10 by tier and density 0.7. Hazards and mistakes are always off.

### `BoardingLayout`

```ts
type BoardingLayout = 'rectangle' | 'aisles' | 'courtyard'
```

Generated Bus Jam floor plan: a solid `rectangle`, `aisles` (a free column every third) or a `courtyard` (a wall down the middle).

### `BoardingLevel`

```ts
interface BoardingLevel
```

A generated level: its configuration, a winning solution and what was measured.

- `seed: number` — The seed asked for.
- `difficulty: BoardingDifficulty` — The tier asked for.
- `parameters: { /** \`'passengers'\` or \`'vehicles'\`. */ mode: 'passengers' | 'vehicles'; /** The floor plan (passenger mode). */ layout: BoardingLayout; /** Buses asked for (passenger mode). */ groups: number; /** Distinct colours. */ colors: number; /** Seats per bus. */ seats: number; /** Waiting spaces or loading bays. */ waitingCapacity: number; /** Later buses' passengers mixed into each turn. */ lookahead: number; }` — The settings used, defaults filled in.
- `config: BoardingConfig` — The level, ready for `createBoardingQueue`.
- `solution: BoardingAction[]` — A replay-checked winning sequence; pass it to `createBoardingQueue` so `solve` can use it.
- `metrics: { /** Moves in the solution. */ items: number; /** Legal moves at the start. */ initialChoices: number; /** Most waiting spaces the solution fills at once. */ certificatePeakWaiting: number; /** Most loading bays the solution fills at once. */ certificatePeakBays: number; /** Buses. */ departures: number; /** Whether the solution really uses the interleaving: fills at least \`lookahead\` waiting spaces (Bus Out: has a bus waiting in a bay when \`lookahead\` > 0). Always true on easy. */ difficultyTargetMet: boolean; }` — What the solution needs, not how hard a person finds it; nothing here claims a shortest plan.

### `BoardingPassenger`

```ts
interface BoardingPassenger extends Cell
```

A coloured passenger standing on a walkable cell (`x` column, `y` row, whole numbers from 0).

- `id: string` — Unique non-empty id; actions and events name it.
- `key: string` — Colour key: the passenger boards only a vehicle with the same key. Non-empty.

### `BoardingState`

```ts
interface BoardingState
```

Where a boarding puzzle stands.

- `remaining: string[]` — Ids still on the board: passengers in the crowd (passenger mode) or buses still parked (vehicle mode).
- `waiting: string[]` — Passenger mode: ids of passengers in the waiting spaces, oldest first.
- `bays: { /** The bus id. */ id: string; /** Seats taken so far. */ loaded: number; }[]` — Vehicle mode: the buses in the loading bays, oldest first, with the seats taken on each.
- `vehicleIndex: number` — Passenger mode: index in `vehicles` of the bus now loading.
- `loaded: number` — Passenger mode: seats taken on the bus now loading.
- `lineIndex: number` — Vehicle mode: index in `passengerLine` of the passenger at the front of the queue.
- `departed: string[]` — Ids of the buses that have filled up and left, in order.
- `moves: number` — Moves played.

### `BoardingVehicle`

```ts
interface BoardingVehicle
```

A bus: its colour and how many passengers fill it.

- `id: string` — Unique non-empty id. In vehicle mode it is also the id of its piece in the traffic layout.
- `key: string` — Colour key: only passengers with the same key board it. Non-empty.
- `capacity: number` — Seats, 1 to 16. The bus departs when every seat is taken.

### `PassengerBoardingConfig`

```ts
interface PassengerBoardingConfig
```

Bus Jam: a crowd on a floor plan, buses arriving in order and a few waiting spaces.

- `mode: 'passengers'` — `'passengers'`: the player taps passengers.
- `width: number` — Board width in cells, 1 to 16.
- `height: number` — Board height in cells, 1 to 24.
- `walkable: Cell[]` — The floor: unique cells inside the board that passengers can stand on and walk through. Any shape.
- `entrances: Cell[]` — Walkable cells where walking paths start (the edge nearest the buses); at least one.
- `passengers: BoardingPassenger[]` — The crowd, 1 to 384 passengers, each on its own walkable cell.
- `vehicles: BoardingVehicle[]` — The buses, 1 to 128, in arrival order. Seats per colour must equal that colour's passengers exactly.
- `waitingCapacity: number` — Waiting spaces for passengers whose bus has not come yet, 0 to 12.

### `VehicleBoardingConfig`

```ts
interface VehicleBoardingConfig
```

Bus Out: a packed lot of buses that must drive out, a few loading bays and one passenger queue.

- `mode: 'vehicles'` — `'vehicles'`: the player taps buses.
- `traffic: TrafficConfig` — The lot, as a `traffic-release` layout: one piece per bus, with its exit routes. No hazards and no mistake limit.
- `vehicles: BoardingVehicle[]` — One bus per traffic piece, matched by id; order does not matter.
- `passengerLine: string[]` — The passenger queue, front first, as colour keys. Seats per colour must equal that colour's passengers exactly.
- `bayCapacity: number` — Loading bays, 1 to 12: how many dispatched buses can wait for their passengers at once.

---

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