---
title: "Grid lane walker: API"
package: "@phaser-ae/grid-walker"
tier: Free
version: 3.0.0-0
released: 2026-10-19
updated: 2026-10-19
description: "A four-way walker for maze and grid games that moves from tile centre to tile centre, with buffered turns, arcade cornering, wrap tunnels and snapshots."
url: https://phaser.io/packs/grid-walker/api
site: Phaser - https://phaser.io
---

# Grid lane walker: API

`@phaser-ae/grid-walker` — A pure four-way walker along the lanes of a tile grid, in tiles: buffered turns, arcade cornering, wrap portals, snapshots.

## The pack

### `gridWalker`

```ts
function gridWalker(): Pack<{ gridWalker: GridWalkerApi }>
```

The `grid-walker` pack: `game.gridWalker`, the pure grid walker. It needs no world; a rules pack imports `createGridWalker` instead. No options.

## Helpers

### `createGridWalker`

```ts
function createGridWalker(config: GridWalkerConfig)
```

Create a headless continuous walker in tile units; wall and portal policies belong to the caller. Throws on an invalid config (see {@link GridWalkerConfig}).

## Classes

### `GridWalker`

```ts
class GridWalker
```

Continuous buffered tile movement with exact centre handling and immediate reversals.

- `readonly config: GridWalkerConfig` — The configuration the walker was created with.
- `constructor(cfg: GridWalkerConfig)`
- `get state()` — A copy of the current pose; changing the copy does nothing to the walker.
- `want(d: GridDirection)` — Buffers the heading to take at the next junction where that turn is open; a full reversal happens at once. Throws if the direction is not up, left, down or right.
- `place(at: GridPoint, direction = this.s.direction)` — Moves the walker to `at` (finite tile coordinates) facing `direction`, default the current heading, and clears any buffered turn and corner alignment. Throws on non-finite coordinates or an invalid direction.
- `tick( dt: number, speed = this.config.speed, onCentre?: (p: GridPoint, d: GridDirection) => GridDirection, onEnter?: (p: GridPoint, d: GridDirection) => void, onTravel?: (part: GridTravel) => void, )` — Advances `dt` seconds at `speed` tiles/s (default `config.speed`) and returns the new state. Movement is split into pieces of at most 1/64 tile and stops exactly at tile centres, so a large frame never skips a decision: - `onCentre(cell, heading)` runs each time the walker sits exactly on a tile centre (not while sliding onto a lane), including every tick it waits there against a wall, and returns the heading to want next, as `want()` would; a ghost's brain picks its turn here. - `onEnter(cell, heading)` runs when the walker's rounded tile changes, or it arrives through a portal: one tile ahead of its next centre, which is when the arcade ghosts look ahead. - `onTravel(part)` reports every piece of the trajectory with its time window in the tick, including the stationary remainder after a wall stop; a portal is a zero-length `portal` piece, never a sweep. Throws when `dt` is outside 0..10 s, `speed` outside 0..10000 tiles/s, or a tick would take over a million pieces.
- `snapshot()` — A copy of the current state, to save; the same as `state`.
- `restore(state: GridWalkerState)` — Replaces the state with a saved one from `snapshot()`. Throws if a direction is invalid, x, y or line is not finite, or align is not "x", "y" or null.

## Types

### `GridDirection`

```ts
type GridDirection = "up" | "left" | "down" | "right"
```

Renderer-independent lane movement. Coordinates are tile centres: integers, one tile = 1 unit.

### `GridPoint`

```ts
interface GridPoint
```

Tile-centre coordinates; one tile is one model unit.

- `x: number` — Column position in tiles; tile centres are integers and x grows to the right.
- `y: number` — Row position in tiles; tile centres are integers and y grows downwards, so "up" is -1.

### `GridTravel`

```ts
interface GridTravel
```

One part of a tick's trajectory. Times are fractions of the tick in [0, 1].
Portal segments have equal start/end times and represent discontinuities, never travel through intervening space.

- `from: GridPoint` — Where this part of the trajectory starts, in tiles.
- `to: GridPoint` — Where this part of the trajectory ends, in tiles; for a portal it is the arrival point.
- `start: number` — When the part starts, as a fraction of the tick from 0 to 1.
- `end: number` — When the part ends, as a fraction of the tick from 0 to 1; equal to `start` for a portal.
- `kind: "move" | "portal"` — `move` for travel through space, `portal` for a jump that crosses no intervening tiles.

### `GridWalkerApi`

```ts
interface GridWalkerApi
```

What the `grid-walker` pack adds to a game: `game.gridWalker`.

- `create: typeof createGridWalker` — Make a walker (see `createGridWalker`).

### `GridWalkerConfig`

```ts
interface GridWalkerConfig
```

Movement speed, blocking predicate, corner windows and optional directed portals.

- `at: GridPoint` — Starting position in tiles; both coordinates must be finite. Tile centres are integers.
- `direction?: GridDirection` — Starting heading; default `left`. Throws if it is not up, left, down or right.
- `speed: number` — Tiles per second; finite and not negative. Throws otherwise.
- `walls: (x: number, y: number) => boolean` — Whether tile (x, y), in integer tile coordinates, blocks movement. Asked for tiles outside any board too, so it must answer for them.
- `turnBefore?: number` — How far before a tile centre, in tiles, a wanted turn may still be taken; 0 to under 0.5, default 0. Throws outside that range.
- `turnAfter?: number` — How far past a tile centre, in tiles, a wanted turn may still be taken; 0 to under 0.5, default 0. Throws outside that range.
- `arcadeAsymmetry?: boolean` — When true, the before and after windows swap for headings that move up or left, reproducing the arcade original's lopsided cornering; default false.
- `portal?: (at: GridPoint, direction: GridDirection) => GridPoint | null` — Directed portal lookup: the tile an actor leaving `at` in `direction` arrives at, or null.
- `portalAt?: "centre" | "edge"` — Where a portal fires. `centre` (default) jumps from the source tile's centre to the destination's centre. `edge` walks on to the source tile's outer edge, jumps to the matching edge of the destination tile and carries the remaining distance on, so a wrap tunnel slides off one side and in from the other without skipping a tile or needing walkable cells beyond the board. The cell beyond the source edge is never tested.

### `GridWalkerState`

```ts
interface GridWalkerState extends GridPoint
```

Current continuous pose, buffered heading and residual diagonal corner alignment.

- `direction: GridDirection` — The heading it is travelling in now.
- `wanted: GridDirection` — The buffered heading it takes at the next junction where that turn is open; equal to `direction` when no turn is waiting.
- `align: "x" | "y" | null` — The axis it is still sliding onto a lane along after a corner turned off-centre, or null when it is on a lane.
- `line: number` — The lane coordinate in tiles that `align` slides to; 0 while `align` is null.

---

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