Brood Engineering

Autonomous construction spiders that build, deconstruct, and upgrade on your behalf.

Overview

Brood Engineering adds small spiderlings that automatically perform construction tasks near you. Simply craft spiderlings, place them in your inventory, and they will:

• Auto-deploy when construction work is detected nearby
• Build ghost entities from your blueprints
• Deconstruct entities and tiles marked for deconstruction
• Upgrade entities marked for upgrade
• Place tiles including landfill and other floor types
• Handle item proxies (module insertion, configuration changes)
• Auto-recall when no work remains

Getting Started

1. Research Brood Engineering (unlocked by catching a fish)
2. Craft Spiderlings (requires electronic circuits, iron plates, inserters, and a raw fish)
3. Place spiderlings in your inventory
4. Place blueprints or mark items for deconstruction
5. Watch your brood work!

Controls

• Alt+B or Shortcut Button: Toggle all spiderlings on/off
  • When disabled, all deployed spiders return to your inventory
  • When enabled, spiders will deploy automatically when work exists

How It Works

Two-Tier Task Assignment

Spiderlings use a smart task assignment system:

1. Anchor Assignment: Your character scans a large area (40 tiles) for work and assigns tasks to idle spiders
2. Self-Assignment: Individual spiders scan their immediate area (8 tiles) and can pick up nearby tasks without returning to you

This prevents wasted trips when there's work near a spider's current location.

Task Priority

Tasks are executed in priority order:

1. Deconstruct entities blocking ghost placement
2. Place foundation tiles (landfill)
3. Build entity ghosts
4. Upgrade entities
5. Handle item proxies
6. Deconstruct remaining entities
7. Place non-foundation tiles
8. Deconstruct tiles

Auto-Deploy & Recall

• Spiders deploy from your inventory when work exists and you're below the maximum count
• Spiders recall to your inventory after being idle near you for 4 seconds
• All spiders teleport to you if you move far suddenly (teleportation, vehicle entry)

Configuration

Access mod settings to configure:

• Show Item Projectiles: Visual effect showing items traveling from your inventory to building spiders

Tips

• Spiders work faster when you're near the construction area
• Keep a stock of spiderlings in your inventory for automatic deployment
• The global toggle (Alt+B) is useful when you need spiders to stop immediately
• Spiders can pick up items on the ground that are marked for deconstruction

Future Plans

This mod is designed with expansion in mind:

• Webs/FOBs: Deployable bases that act as spider anchors with their own inventory
• Spider Castes: Specialized spiders (builders, cutters, haulers, crafters)
• Mother Zero: Transform into the brood mother - a spidertron that cannot handcraft

Compatibility

Built for Factorio 2.0. Should be compatible with most mods. If you encounter issues, please report them.

Credits

Inspired by the Spiderbots mod by asher_sky. Rebuilt from scratch with a cleaner architecture for extensibility.

Development

Running tests (FactorioTest)

This repo includes a small in-game test suite under tests/ that runs via FactorioTest.

Prerequisites:

• Factorio 2.0 installed locally.
• bun installed via mise (see .mise.toml).
• Node 18+ available on PATH (needed because FactorioTest CLI currently calls npx fmtk internally).

Setup:

1. Install tools: mise install
2. Install dev dependencies: bun install
3. Run tests: bun run test:factorio -- --factorio-path /path/to/factorio

Notes:

• The CLI creates an isolated data dir at ./factorio-test-data-dir by default.
• Only brood-engineering and factorio-test are enabled unless you pass --mods ... (we enable elevated-rails + quality + space-age by default in package.json / .mise.toml so many shared blueprints import).
• Extra args after -- are forwarded to Factorio (e.g., --disable-audio --graphics-quality low).
• On macOS app bundles, FactorioTest CLI may generate an incorrect read-data path. If you see “There is no package core…”, edit factorio-test-data-dir/config.ini to use read-data=__PATH__executable__/../data (or an absolute path to factorio.app/Contents/data). The CLI will keep that line on subsequent runs.