---
title: "Destructible cover: API"
package: "@phaser-ae/destructible-cover"
tier: Pro
version: 3.0.0-3
released: 2026-10-14
updated: 2026-10-20
description: "Shields, walls and breakable terrain made of cells with their own materials and health, that shots trace through and explosions chip away by stencil, radius or rectangle."
url: https://phaser.io/packs/destructible-cover/api
site: Phaser - https://phaser.io
---

# Destructible cover: API

`@phaser-ae/destructible-cover` — Authored material masks, swept box contacts, explosion-stencil splats and shield erosion as in Space Invaders.

## The pack

### `destructibleCover`

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

Install the renderer-independent destructible cover API.

## Helpers

### `bunkerPreset`

```ts
function bunkerPreset( options: { count?: number; worldWidth?: number; /** Top edge of the bunkers. */ y?: number; cellSize?: number; hp?: number; mask?: readonly string[]; /** Left x of the first bunker and gap between bunker left edges; default spreads them evenly. */ left?: number; pitch?: number; } = {}, ): CoverDefinition[]
```

Evenly spaced bunkers of any authored mask (default: the Space Invaders shield at one unit per pixel).

### `createDestructibleCover`

```ts
function createDestructibleCover(definitions: CoverDefinition[] = [])
```

Create independent damageable masks, or empty cover for a game without shields.

### `INVADERS_ALIEN_SPLAT`

```ts
const INVADERS_ALIEN_SPLAT: readonly string[]
```

The alien-shot explosion stencil (ROM AShotExplo, $1CDC, upright): a ragged 6-wide, 8-tall splat.

### `INVADERS_PLAYER_SPLAT`

```ts
const INVADERS_PLAYER_SPLAT: readonly string[]
```

The player-shot explosion stencil (ROM ShotExploding, $1C91, upright): a ragged 8 x 8 splat.

### `INVADERS_SHIELD_MASK`

```ts
const INVADERS_SHIELD_MASK: readonly string[]
```

The Space Invaders shield, 22 x 16 pixels, upright (from the ROM's ShieldImage at $1D20, which is
stored rotated): a flat top with chamfered corners and a notch cut into the base.

## Classes

### `DestructibleCover`

```ts
class DestructibleCover
```

Owns mask health and swept contacts through surviving cells; destroyed cells become transparent.

- `readonly definitions: CoverDefinition[]` — The validated definitions (a private copy).
- `constructor(definitions: CoverDefinition[])`
- `get revision()` — Increments whenever any cell's health changes; renderers can redraw only when it moves.
- `cells(id?: string): CoverCell[]` — Surviving cells of one definition or all of them.
- `runs(id?: string): CoverRun[]` — Surviving cells merged into horizontal runs of equal material and health.
- `cellHealth(id: string, col: number, row: number)` — Health of one cell (0 when destroyed, empty or outside the mask).
- `trace(from: Cell, to: Cell, radius = 0): CoverContact | null` — Earliest swept contact for a point/circle approximated as a square of half-size `radius`.
- `traceBox( from: Cell, to: Cell, halfWidth: number, halfHeight: number, ): CoverContact | null` — Earliest swept contact for an axis-aligned box of half extents `halfWidth`/`halfHeight` moving from `from` to `to`, through actual surviving cells only, so holes stay transparent. `t` is 0..1.
- `damage(contact: CoverContact, amount = 1, blastRadius = 0)` — Damage the contacted cell by `amount` and every surviving neighbour whose centre is within `blastRadius`.
- `splat(at: Cell, splat: CoverSplat, amount = Infinity)` — Stamp an explosion stencil at a world point on every cover it overlaps. A cover cell is damaged when its centre falls inside a set stencil cell. `amount` defaults to Infinity (erase), divided by each material's blastResistance; indestructible cells survive.
- `eraseRect( rect: { x: number; y: number; w: number; h: number }, amount = Infinity, )` — Damage every cell overlapping a world rectangle, e.g. an invader marching through a bunker.
- `drain()` — Take damage events not returned yet.
- `snapshot()` — Health of every cell.
- `restore(s: Record<string, number[]>)` — Restore health from a snapshot of the same definitions.
- `reset()` — Restore every cell to full health.

## Types

### `CoverCell`

```ts
interface CoverCell extends Cell
```

One surviving mask cell with its world position (top-left), authored material and current health.

- `id: string` — Owning definition id.
- `col: number` — Mask column.
- `row: number` — Mask row.
- `size: number` — Cell size.
- `material: string` — Mask character.
- `hp: number` — Remaining health.

### `CoverContact`

```ts
interface CoverContact
```

The earliest swept hit, including mask indices and interpolated contact position.

- `cover: string` — Definition id hit.
- `col: number` — Mask column hit.
- `row: number` — Mask row hit.
- `t: number` — Fraction of the sweep at contact, 0..1.
- `at: Cell` — Swept centre at contact.

### `CoverDamageEvent`

```ts
interface CoverDamageEvent
```

One cell's health change.

- `cover: string` — Definition id.
- `col: number` — Mask column.
- `row: number` — Mask row.
- `remaining: number` — Health left.

### `CoverDefinition`

```ts
interface CoverDefinition
```

An arbitrary rectangular material mask positioned in renderer-independent model units.

- `id: string` — Unique id.
- `x: number` — Left edge of mask column 0.
- `y: number` — Top edge of mask row 0 (y grows downward).
- `cellSize: number` — World size of one mask cell.
- `mask: string[]` — Equal-width rows; `.` and space are empty, every other character names a material.
- `materials: Record<string, CoverMaterial>` — Material per mask character.

### `CoverMaterial`

```ts
interface CoverMaterial
```

Durability, blast resistance and optional permanent blocking for one mask character.

- `hp: number` — Health of one cell of this material.
- `blastResistance?: number` — Divides splash damage from blasts and splats (direct hits are undivided). Default 1.
- `indestructible?: boolean` — Blocks traces but never loses health.

### `CoverRun`

```ts
interface CoverRun extends Cell
```

A horizontal run of adjacent surviving cells with one material and one health value, for cheap drawing.

- `id: string` — Owning definition id.
- `row: number` — Mask row.
- `col: number` — First mask column.
- `length: number` — Cells in the run.
- `size: number` — Cell size.
- `material: string` — Mask character.
- `hp: number` — Health shared by the run.

### `CoverSplat`

```ts
interface CoverSplat
```

An explosion stencil. Every non-empty mask cell (any character except `.` and space) is a pixel of
damage; the stencil is centred on the blast point unless `anchor` (in stencil cells) says otherwise.
Space Invaders' shot explosions are splats like this: a ragged 8x8 or 6x8 pattern, not a circle and
not a single cell.

- `mask: string[]` — Stencil rows; any character but `.` and space damages.
- `cellSize?: number` — World size of one stencil cell. Default: the damaged cover's own cellSize.
- `anchor?: Cell` — Stencil cell placed on the blast point. Default: the stencil centre.

---

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