Chapter 02 · 5 min read
How the island decides
Twenty rules, a director with a sense of drama, and why a library has to wait for three houses.
Every day the routine asks the same question: what could happen next? The answer is never "anything". It is a list of changes that are legal right now, computed by rules.ts.
Three kinds of change
- Ground – the terrain of one tile changes. Sand rises from the sea, sand turns into meadow, rock breaks through, trees grow into forest.
- Structures – something is built on a free tile: a tree, a house, a path, a well, a jetty, a lighthouse …
- Life – someone moves into a house, or an animal settles on the ground it likes.
Everything waits for something
The interesting part are the dependencies. A few examples:
- The very first meadow needs sand on all four sides – grass never grows on the coast.
- A house needs land on three sides and keeps a tile of space to its neighbours. After the first house, new ones stay within three tiles of the village.
- The library waits for three houses and wants to stand next to a path.
- The harbour needs a sandy coast, three houses and a jetty nearby.
- The lighthouse needs rock by the sea – and a house for its keeper.
- Ruins only surface far away from every house, once the island is big enough to have forgotten something.
Inhabitants have trades, and trades have conditions too: a keeper only arrives once there is a lighthouse, a farmer needs a field, a miller needs a windmill.
| Change | Rule |
|---|---|
| Land | Sand rises from open water that touches the island on at least one side, never closer than two tiles to the edge of the map. |
| Meadow | Sand turns to grass only inland (no open water on any side) and only next to existing grass – the very first meadow needs sand on all four sides. |
| Rocks | Rock breaks through bare sand or grass on the coast, or grows inland from rock that is already there. At most one rock per twelve tiles of land. |
| Forest | Bare grass becomes forest when at least two trees or forest tiles surround it. Forest may cover at most a quarter of the land. |
| Tree | A tree needs a free grass tile. |
| House | A house needs a free grass or sand tile with land on at least three sides and no other house directly next to it. Every house after the first stands at most three tiles from a house or path. |
| Path | Paths appear once there are two houses. A path tile must touch a house, a path or a public building, and paths never form a 2×2 square. |
| Field | A field needs a free grass tile at most three tiles from a house and two inhabitants to work it. At most two fields per house. |
| Garden | A garden sits on free grass directly next to a house. One garden per house. |
| Well | A well needs two houses, a spot at most two tiles from a house and no other well within five tiles. |
| Jetty | A jetty is built into the water next to a sandy shore, with a house at most six tiles away. At most three jetties. |
| Boat | A boat needs someone to sail it and moors in open water next to a jetty or the harbour. One boat per jetty or harbour. |
| Harbour | The harbour needs a sandy coast tile, three houses and a jetty within three tiles. There is only one. |
| Lighthouse | The lighthouse needs rock on the coast and at least one house for its keeper. There is only one. |
| Library | The library needs at least three houses and free grass directly next to a path. There is only one. |
| Windmill | A windmill needs free grass with two fields within three tiles. At most two. |
| Market | The market needs five houses and a free tile touching at least two path tiles. There is only one. |
| Ruin | Ruins of an older time surface on forest, rock or grass at least five tiles from any house, once the island has thirty tiles of land. At most two. |
| Inhabitant | An inhabitant moves into a house with room (two per house). Their trade must fit the island: a keeper needs the lighthouse, a farmer a field, a fisher a jetty, boat, harbour or a house on the beach. |
| Animal | An animal needs a free tile of the ground it likes (sheep on grass, goats near rock, foxes and deer in the forest, gulls and crabs on the beach, cats and dogs near a house). At most one animal per eight tiles of land. |
The director
Claude chooses the daily change, but the island also has a rule-based director that can decide on its own. It weighs what the island needs – room to build, people for empty houses, a first harbour once it becomes possible – adds a little variety (no three houses in a row) and draws one option. The director is deterministic: the same island on the same day always gets the same suggestion.
The director is the safety net. Its suggestion is part of the daily plan, and if the routine cannot make a good choice, it lets the director decide. Those days are marked auto in the logbook.