terrarium

The simulation

How it works

A day in Terrarium: what each person knows, how they decide, and how a whole world's choices resolve at once.

Terrarium runs in days. On every day, every person looks at their surroundings, decides what to do, and the world applies everyone’s choices together.

A person

Each person is built in layers, from what never changes to what changes every day.

IDENTITY        personality (five traits), values, one life aspiration
   │
BELIEFS         where food is, who can be trusted, whose land this is
   │            (learned from experience, and possibly wrong)
   │
TODAY           what they can see, what they need, what they're about
   │
ACTION          move, gather, eat, rest, share, court, build, claim, fight…

Identity is stable: a simplified Big Five personality, a few core values and one aspiration, such as to be respected, to protect those around them, or to explore. Beliefs update from what happens to them and what others tell them, so they can be out of date or plain wrong. Memory keeps the episodes behind those beliefs: who gave them food, who attacked them, who courted them.

A day

  1. The world turns. Plants and wood regrow, herds breed and wander, food spoils, the season and weather change, illness spreads between neighbours.
  2. Everyone looks. Each person sees a few cells around them, the people nearby (how hungry, hurt or well supplied they look) and what’s on the land.
  3. Everyone decides. A language model thinks the day through for them, or, without one, they act on instinct.
  4. Everything resolves at once. All choices are applied together against the same morning. Walking away doesn’t dodge a blow struck the same day.
  5. Beliefs update. People remember what they did and what was done to them, and what they saw done to others.

The world never decides for anyone

This is the rule everything else follows. The engine applies the physics of what people do: the damage of a blow, the food taken, the shelter finished. It updates what they perceive and believe. It never chooses on anyone’s behalf: no automatic defence, no allies stepping in unasked, no land that refuses a stranger. A claim to land is a belief. Whether to respect it, defend it or ignore it is up to the people involved.

Watching

Every action becomes an event. The viewer shows the world as it unfolds; the full log, a readable chronicle and periodic snapshots are written out for analysis, so a run can be replayed and its turning points traced back to their causes.