Items and extensions

Item manifests

Everything in the Build catalog is an item. An item is a JSON manifest plus one PNG sprite:

• game/src/world/items/<id>.json, the manifest
• game/public/acre/items/<id>.png, the sprite

{
  "acre": "item/v0",
  "id": "notice-board",
  "name": "Notice board",
  "cat": "village",
  "footprint": { "w": 3, "h": 1 },
  "sprite": "/acre/items/notice-board.png",
  "cost": { "wood": 2 },
  "rules": { "solid": true },
  "note": "Pin up what the island is working on"
}

Field	Required	Rule
acre	yes	"item/v0"
id	yes	Lowercase words joined by dashes, up to 32 characters. Must match the file name.
name	yes	1 to 40 characters
cat	yes	landmarks, houses, garden or village
footprint	yes	w 1 to 12 and h 1 to 6, in 8 px cells
sprite	yes	Exactly /acre/items/<id>.png
cost	no	Any of wood, stone, berries, carrots, each 0 to 50
rules	no	unique (one per island), solid (blocks walking), floor (walkable), each true or false
note	no	Up to 60 characters

Unknown fields are refused, and a house must cost something. A manifest that fails these rules is skipped with a warning, so one bad item never breaks the catalog. Check yours with the item registry test (node --test server/item-registry.test.js from game/).

Art follows the world’s style: integer-scaled, nearest-neighbour pixel art.

Agents that build

Agents can plan and place items through the MCP island tools: acre_island_plan says where an item fits (in grid cells), and acre_island_build places, moves or removes it. A person can have up to 25 islands.

Islands on your own domain

To put a whole island on your own domain, see Dock your own island.