Agent skill

object

Interactable things in the world — the atoms of adventure

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npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/object

SKILL.md

Object

"Everything is an object. Objects have slots. Slots hold data OR behavior." — Dave Ungar, Self: The Power of Simplicity

What Is It?

An Object is anything you can interact with in the adventure world. Keys, lamps, chests, furniture, food, tools — all objects.

Objects are the atoms of the adventure. They:

  • Have an identity (id, name, description)
  • Advertise their actions (The Sims style)
  • Contain state (lit, fuel, uses)
  • Inherit from prototypes (Self style)

The Sims Architecture

From Will Wright's SimAntics:

"The intelligence is in the objects, not the characters."

Objects advertise what they can do:

yaml
advertisements:
  LIGHT:
    description: "Light the lamp"
    score: 80
    guard: "lamp has fuel"
    effect: "Darkness retreats"

The character picks from what's advertised. No hardcoded behavior.

Self-Style Prototypes

Objects inherit from prototypes:

yaml
inherits:
  - skills/objects/light-source.yml
  - skills/objects/takeable.yml

A lamp inherits "light-source" behaviors without copying them.

Object Properties

Property Purpose
id Unique identifier
name Display name
type Category (item, furniture, tool)
description What player sees
examine Detailed look
takeable Can be picked up
container Can hold things
contains What's inside
state Mutable properties
advertisements Available actions
inherits Prototype chain

State

Objects have mutable state:

yaml
state:
  lit: false
  fuel: 100
  uses_remaining: 3

State changes are tracked in YAML. The adventure is the save game.

Simulate — Object Update Loops

THE SIMS INSIGHT: Objects manage their own simulation!

Every object can have a simulate property — a natural language description of what happens each turn. The compiler generates a closure that receives world.

yaml
simulate: |
  if lit:
    consume_fuel(1)
    if fuel <= 0:
      extinguish()
      emit("The lamp sputters and dies!")

This compiles to:

javascript
simulate_js: (world) => {
  if (world.object.state.lit) {
    world.consume_fuel(1);
    if (world.object.state.fuel <= 0) {
      world.extinguish();
      world.emit("The lamp sputters and dies!");
    }
  }
}

Resilience — The SimCity Zone Pattern

WILL WRIGHT INSIGHT:

"SimCity zones are self-healing. If one tile burns but the center survives, the zone will eventually rebuild."

Simulation functions should be:

1. Robust — Handle Missing Data

javascript
// BAD: crashes if state is undefined
if (world.object.state.fuel > 0) { ... }

// GOOD: defensive access
if ((world.object.state?.fuel ?? 0) > 0) { ... }

2. Self-Initializing — Create Default State

yaml
simulate: |
  first ensure state.lit exists (default false)
  ensure state.fuel exists (default 100)
  then proceed with normal simulation

The compiled code initializes missing state:

javascript
simulate_js: (world) => {
  const state = world.object.state ??= {};
  state.lit ??= false;
  state.fuel ??= 100;
  // Now safe to proceed...
}

3. Self-Healing — Recover from Corruption

yaml
simulate: |
  if fuel is somehow negative, reset to 0
  if lit but fuel is 0, extinguish (inconsistent state!)
  if broken flag is set but durability is full, clear broken

The compiled code heals invalid states:

javascript
simulate_js: (world) => {
  const state = world.object.state;
  // Heal negative values
  state.fuel = Math.max(0, state.fuel);
  // Heal inconsistency
  if (state.lit && state.fuel <= 0) {
    state.lit = false;  // Self-heal
    world.emit("The lamp was somehow lit without fuel — fixed.");
  }
}

The defaults Field

Objects can declare their default state values:

yaml
object:
  id: brass-lantern
  defaults:
    lit: false
    fuel: 100
    durability: 100
  simulate: |
    ensure all defaults are initialized
    ...

The runtime merges defaults into state before simulation.

Methods — Named Behaviors

Objects can define named methods that simulate or advertisements can call. Natural language → compiled closures. 1:1 mapping!

yaml
methods:
  consume_fuel: "reduce fuel by amount, minimum 0"
  extinguish: "set lit to false, emit darkness event"
  ignite: "set lit to true if fuel > 0"

Compiles to:

javascript
methods_js: {
  consume_fuel: (world, amount) => { 
    world.object.state.fuel = Math.max(0, world.object.state.fuel - amount); 
  },
  extinguish: (world) => { 
    world.object.state.lit = false; 
    world.emit('DARKNESS'); 
  },
  ignite: (world) => { 
    if (world.object.state.fuel > 0) world.object.state.lit = true; 
  }
}

The Power of 1:1 Methods

  • Method name in natural language = method name in JS/PY
  • consume_fuel(1) in YAML → world.consume_fuel(1) in JS
  • Methods compose — extinguish() can call other methods
  • Advertisements can call methods in their effect

The Complete Pattern

Object
├── state         (mutable data)
├── simulate      (per-turn update)
├── methods       (named behaviors)
└── advertisements (player actions)

Advertisements call methods. Simulate calls methods. Methods update state.

Everything flows through compiled closures over world.

Advertisements (Actions)

Each advertisement can have:

yaml
LIGHT:
  description: "Light the lamp"           # What it does
  score: 80                               # Base attractiveness
  score_if: "player is in dark room"      # When to boost
  guard: "lamp has fuel"                  # Can you do it?
  effect: "Lamp is now lit"               # What happens

Natural language fields (score_if, guard, effect) are compiled to JS/PY.

Containers

Containers hold other objects:

yaml
container: true
contains:
  - brass-key
  - old-map
capacity: 10
locked: true

Examples

Simple Item

yaml
object:
  id: brass-key
  name: "Brass Key"
  emoji: "🔑"
  description: "A heavy brass key."
  takeable: true

Lamp with State

yaml
object:
  id: oil-lamp
  name: "Oil Lamp"
  emoji: "🪔"
  state:
    lit: false
    fuel: 100
  advertisements:
    LIGHT:
      guard: "fuel > 0 AND not lit"
      effect: "The lamp flickers to life."

Locked Chest

yaml
object:
  id: treasure-chest
  name: "Treasure Chest"
  container: true
  locked: true
  contains:
    - gold-coins
    - magic-ring
  advertisements:
    UNLOCK:
      guard: "player has chest-key"
      effect: "The lock clicks open."

Related Skills

Protocol Symbol

SIMANTICS — The Sims behavioral architecture

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