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Destructible cover

Pro packv3.0.0-32DArcade

Cover that wears away the way arcade bunkers do: masks of square cells, each with its own material and health, that shots trace through and explosions chip away. Shapes, materials and blast patterns are all yours to author.

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Released October 14, 2026 · updated October 20, 2026

Destructible cover: a screenshot of its demo
A note about these graphics

Expansion packs don't come with graphics. This screenshot is one way of drawing what the pack does, made for its demo: none of the sprites, tiles or backgrounds in it are in the pack.

That's by design. A pack is a game's logic, mechanics and effects, and it works with whatever art you give it. Some packs draw effects, backdrops or 3D scenes of their own, but none carries a game's sprites.

So the look is yours. Make the art on phaser.io, bring your own, or let your agent draw it in code: the same pack can look like anything.

What it does

A piece of cover is a mask: rows of characters, one per cell, each character standing for a material with hit points, an optional blast resistance, or no damage at all. You lay out as many pieces as you need, of any shape and size. When a shot moves, you trace its box or point from where it was to where it is, and get back the earliest contact with a cell that still stands. Holes are real: a shot passes straight through a gap an earlier shot opened.

Damage comes three ways. splat erodes by a stencil, a small mask of its own, so a shot blows a ragged hole out of a shield rather than one cell or a perfect circle. damage hits the contacted cell and spreads to neighbours within a radius, divided by each one's blast resistance. eraseRect damages everything under a rectangle, for an enemy marching through a shield. Indestructible cells block traces and never take damage, so a frame can hold its shape while the brick inside crumbles.

For drawing, runs() returns horizontal runs of cells with the same material and health, so a shield is a handful of rectangles rather than hundreds of cells, and revision changes on every hit so you redraw only when something broke. Snapshots save the state of every cell, and the whole thing runs without a renderer.

Features

  • Masks and materials — cover authored as rows of characters, each character a material with hit points, blast resistance or indestructible.
  • Swept traces — traceBox and trace find the earliest contact with a surviving cell along a shot's path, and only visit the cells under it, so small shots against large masks stay cheap.
  • Three kinds of damage — stencil splats, radius blasts scaled by resistance, and rectangle erasure.
  • Arcade presets — INVADERS_SHIELD_MASK, the classic 22 by 16 shield with its off-centre notch, and INVADERS_PLAYER_SPLAT and INVADERS_ALIEN_SPLAT, the ragged shot explosions, taken from the original game's data.
  • Evenly spaced bunkers — bunkerPreset places any number of bunkers of any mask across a screen.
  • Cheap drawing — runs() merges cells into horizontal runs, and revision tells you when to redraw.
  • Snapshot and reset — save, restore and reset every cell's health.

Good for

  • Fixed shooters with bunkers in the style of Space Invaders, with shields eroded by player and alien shots and by invaders marching through.
  • Castle and fortress walls that crumble brick by brick behind an indestructible frame.
  • Top-down shooters with cover that wears away as the fight goes on.
  • Artillery and digging shots, where a projectile bites a shaped hole out of a wall.
  • Armour plates of several materials, where heavy plating shrugs off splash that destroys brick.

Make it yours

Each definition has an id, a position, a cell size, a mask and the materials its characters stand for. There is no limit on how many definitions, shapes, materials or stencils you use, and contact sizes and damage amounts are the caller's to choose per shot. bunkerPreset takes the count, world width, height on screen, cell size, hit points, mask, left edge and spacing.

Two materially different uses: the four classic shields, eroded by the original shot stencils and erased where the invaders march; and a fortress of steel that never breaks, armour with three hit points and a blast resistance of two, and one-hit brick, all worn down by radius blasts.

A quick look

Four bunkers, a shot traced upward, a splat where it hit, and the shields drawn as runs:

const dc = game.destructibleCover;
const cover = dc.createDestructibleCover(dc.bunkerPreset({ count: 4, worldWidth: 224, y: 192, left: 32, pitch: 45 }));
const hit = cover.traceBox({ x: 30.5, y: 210 }, { x: 30.5, y: 206 }, 0.5, 2);   // a 1x4 shot moving up
if (hit) cover.splat({ x: hit.at.x, y: hit.at.y - 4 }, { mask: [...dc.INVADERS_PLAYER_SPLAT] });
for (const r of cover.runs()) drawRect(r.x, r.y, r.length * r.size, r.size, r.material, r.hp);

Works with

Good to know

  • Cells are axis-aligned squares and do not collapse or fall: there is no physical crumbling.
  • It is not for continuous deformable terrain meshes.
  • Masks must be non-empty and rectangular, at most a million cells each.
  • A snapshot only restores into definitions with the same mask shapes.

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