ProLibertateGames/docs/RULES-catan-seafarers.md

Katan: Seafarers

Seafarers is an expansion switched on at setup (CatanOptions.expansions; the old single ruleSet in saves is still read) and its map is chosen beside it (CatanOptions.scenario). It is the base game (RULES-catan.md) with a sea, ships, a pirate, gold fields and islands to settle. Code: game/catan/CatanSeaRules.kt (the additions), CatanSeaBoard.kt (the map), CatanBoard.kt (Topology, the geometry shared by every map), state behind CatanState.sea (null in the other rule sets). It can be combined with Cities & Knights; see With Cities & Knights below.

Where the published rules leave room, or where this game differs, it says so below.

The maps

Each map is a fixed arrangement of land and sea; the resources on the plain hexes, the number tokens and the nine harbours are shuffled for each game. The red numbers (6, 8) are never on neighbouring hexes. Players take three or four seats; the default target is 12 points (menu: 8, 10, 12, 14). Pick the map at setup; each scenario names where the starting settlements may go (SeaStart).

• Heading for New Shores (default). A large home island (21 hexes, one desert) and three small islands (3, 3 and 2 hexes) across the water, with gold fields on two of the small ones. Start on the home island.

• Four Islands. Four equal islands (six hexes each) and two one-hex gold islets between them. Each player may start on any of the four main islands, so a table can spread out or crowd one; the islets are the prize for the first ship to arrive.

• Through the Desert. One 25-hex island cut across by a broad desert (seven hexes that pay nothing and hold the robber), with three islets and gold to sail to. Everyone starts on the island. The desert is land, so a road can cross it, but nothing beside it pays, which is what makes the far side a race.

• The Fog Islands. A 13-hex home island (one desert), a two-hex islet and a 14-hex bank of fog. See Fog below.

• Cloth for Catan. A 17-hex main island, an eastern isle, two islets, and four villages on the coast. See Cloth below.

• The Forgotten Tribe. A 17-hex home island and three isles carrying four tribe chips. See The Forgotten Tribe below.

• Pirate Islands. An 18-hex home island and two isles (five and four hexes) each held by a pirate fortress. See Pirate Islands below.

• Wonders of Catan. A 13-hex island with a desert, a 12-hex island, and gold islets. See Wonders below.

• The Treasure Islands (Catan Universe extra). A 15-hex home island and four fog isles, eight hexes of fog in all. See Catan Universe extras below.

• The Oases (Catan Universe extra). One 37-hex island that is mostly desert, with three oases hidden in it.

• The Great Canal (Catan Universe extra). A 25-hex island split by a row of five canal tiles, and gold islets.

A new island for the bonus is any island that is not a starting island for that map.

The geometry is the same lattice as the base island, generalised (Topology): a hex is land or sea, a crossing can hold a town if any hex touching it is land, an edge can hold a road if any hex touching it is land and a ship if any hex touching it is sea (so a coastal edge takes either, never both).

What changes

Setup. Both starting settlements (and their roads) go on the home island. A starting piece is a road, never a ship. The second settlement collects from the hexes round it as usual (gold pays nothing at setup).

Ships. A ship costs 1 lumber and 1 wool and lies on a sea edge.

• It must join your fleet or a town of yours: one end of the edge touches your town, or another of your ships. An opponent's town is a wall.
• Roads and ships connect only at a town of your own: a road cannot start from a ship's end, nor a ship from a road's, unless a settlement or city of yours stands on that crossing. A settlement may be built at the end of a ship route exactly as at the end of a road route.
• No more than 15 ships. Road Building may lay two roads, two ships or one of each.
• Sailing. Once per turn you may move one ship, never one built or moved this turn, and only a ship at the open end of a route (one end touches nothing else of yours). It goes to any edge it could be built on with it lifted off.

The pirate. Starts in the open sea. On a seven (and with a Knight card) the player moves either the robber, to any land hex, or the pirate, to any sea hex. The robber works as before. The pirate blocks the six edges round its hex: no ship may be built or sail onto them (ships already there stay). It robs one card at random from a player with a ship on an edge of its hex.

Gold. A gold field has a number like any hex. When it comes up, each town beside it (one card; a city two) pays its owner any resource of their choice, chosen after the ordinary production is dealt, in seat order from the roller. The robber blocks a gold field like any hex. If the bank cannot supply the choice it is limited to what it holds.

New islands. The first player to settle on each island other than the home island scores 2 bonus points, permanently (SeaState.islandBonus). A second settlement there earns nothing extra.

Longest route. Longest Road counts roads and ships together, as a path of your pieces that never runs through an opponent's town and changes between road and ship only at a town of yours. Five or more, as before.

Everything else (development cards, trading, harbours, Largest Army, the discard on a seven) is the base game.

Fog

Fog hexes (Terrain.FOG) are land that is face down. Under them is a shuffled pile of tiles (SeaState.fogDeck): resources, with one gold field in every five, each with its number token. The pile is hidden from every seat but the host's, like the development deck.

• Finding. When a road or ship is built (or a ship sails) and an end of it touches a fog hex, the hex is turned over, taking the next tile and its number. Several hexes can be found by one piece.
• The find pays. The finder takes one card of what lies there, supply permitting; a gold field lets the finder choose any resource (the gold choice, resuming Road Building if that is what was under way).
• Until then nothing produces there, nobody may start beside it, and the robber cannot go on it.
• Differences from the published scenario. The fog here is always land: the physical tiles can turn out to be sea, but the board's land and sea are fixed in the geometry, so a found hex never turns to water. Fog is also on one bank rather than between several islands, and the number tokens are dealt with the tiles, so two red numbers can end up side by side once found.

Cloth

The published scenario puts cloth villages between the islands and pays cloth when a village's number is rolled. This implementation is the author's reading of that, not a transcription of the printed rules:

• A village is a land hex with a number token and a stock of cloth (6). It produces no cards and nothing may be built on it, but its corners can hold settlements like any other hex's.
• When its number rolls, the village pays one cloth token to each settlement or city beside it (a city is worth no more than a settlement here), until the stock is gone. If the stock is short, the seats nearest the roller, in turn order, take what is left. The robber on a village stops it; the pirate does not.
• Two cloth are a victory point (an odd token is worth nothing alone). Tokens are scored, not spent, and not tradeable.
• Works with Cities & Knights: the village pays after the dice, before the aqueduct and gold.

The Forgotten Tribe

Also the author's reading. A chip lies face up on four hexes of the small isles (the hexes are marked on the board). The chips are dealt at the start of the game, one of each kind in turn:

• The first settlement built on a crossing beside a chip hex takes that chip; it is gone for everyone else. (The setup settlements are never beside one, since the home island is the only start.)
• A point chip is one victory point. A harbour chip lets that seat trade 3:1 at the bank, wherever it is. A gold chip pays two resources of the settler's choice, taken at once like gold.
• The chips come on top of the island bonus for being first to a new island.

Pirate Islands

The author's reading of the scenario; the printed one uses knights and a roaming pirate fleet, which this does not.

• A fortress is a land hex with no number and a strength of 3. Nobody may build a settlement on any crossing of an island that still has a standing fortress. Roads and ships may go there.
• A seat with a ship beside a fortress may raid it in its turn for 1 ore, 1 wool and 1 grain, as many times as it can pay. Each raid takes one point of strength.
• The raid that takes the last point takes the fortress: the hex becomes desert (no number, robber may sit there), the island is open to settle for everyone, and the taker gets 2 victory points. The robber never sits on a standing fortress.
• The island still counts as a new island for the first-landing bonus.

Wonders

Also the author's reading. Every seat may build one wonder in four stages, once it has a city anywhere on the board. Each stage is one move costing cards (stage 1: 2 brick, 1 lumber, 1 grain; 2: 1 brick, 2 ore, 1 wool; 3: 3 ore, 1 grain, 1 lumber; 4: 3 ore, 2 grain, 1 brick). Each stage built is one victory point, and the seat that builds the fourth stage wins at once, whatever the point target. Wonders are not shared: each seat has its own.

Catan Universe extras (inferred)

These three exist in the Catan Universe app but not in the physical set. Only their names, menu texts and log lines could be read (docs/RE-catan-universe.md); the rule values are compiled code that was not recovered. Every rule below is inferred from those names and texts, not copied.

• Treasure Islands. The app's text: "Treasures await the Catanians on neighboring, fog-covered islands. Discoveries are rewarded!" Its chest rewards (log texts and action names) are bricks, wool and grain; a resource of choice; a development card; two roads. Here: up to five chests are dealt face down to random fog hexes at the start. A seat that uncovers the hex (the fog rules) opens the chest at once and takes: a brick, a wool and a grain; one resource of its choice (a gold pick); a development card (a resource of choice if the deck is empty or it is Cities & Knights, which has no deck); or two lumber and two brick standing in for two free roads (the free-roads phase would have to nest inside a ship move). The app's Cities & Knights version gives a progress card; that is not modelled. The app's fixed treasure bonus (SEAFARER_TREASURE_BONUS) is not modelled either.
• The Oases. The app's text: an enormous desert with rumoured oases and treasures, base-game rules. Here: the oases are fog hexes inside the desert, uncovered by a road reaching them, and hold the same chests as above. There is no ship rule on the map itself.
• The Great Canal. The app's text, for Cities & Knights plus Seafarers: build a canal; first to 21 (3 players) or 18 (4 players) wins; the canal's parts earn victory points; when a tile is dug out, grain grows there. Its knights dig in the app; here digging is cheaper to implement and play without Cities & Knights: a canal tile is a desert hex with its number token hidden. A seat with a settlement or city on a corner of the tile digs one unit for 1 brick and 1 ore; three units finish the tile, which becomes fields with the hidden number. Every two units a seat has dug are a victory point. The app's gold river, harbour changes and target scores are not modelled.

With Cities & Knights

Switching both expansions on plays Cities & Knights on any Seafarers map (CatanState.ck and CatanState.sea both set; the target menu is 10, 12, 14 or 16, default 14). Where the two meet, this game decides as follows:

• Ships cost 1 lumber and 1 wool as before and are built and sailed in a turn like a road, including with the Road Building progress card (roads and ships, as in Seafarers).
• Knights stand on land crossings at the end of one of your roads or ships, and walk along that same network. A crossing that touches only sea is never a knight post.
• The pirate sleeps with the robber: only after the first barbarian attack does a seven let the player move the robber (to land) or the pirate (to sea). The pirate robs one good, resource or commodity, from a seat with a ship beside it. The bishop moves the robber only.
• Gold pays after the roll and before the aqueduct and any other chore: a settlement beside it chooses one resource, a city two. (A city on gold takes two resources, not a resource and a commodity.)
• Scoring. First-landing bonus points are added to a seat's points like any other; the barbarians count cities wherever they stand, island or not.
• Merchant goes only on a land hex; Fog works as in Seafarers (a find pays a resource card).

Not included

The physical expansion has more scenarios and the Catan Universe app adds more still. These are out of scope here: the Explorers & Pirates combination, the printed rules of the wonders and pirate-islands scenarios (the versions here are simplified) and trade ships. Drought and the app's other scenarios (Six Islands, Oceania, Great Catan, Enchanted Land, the Inka and Big Game sets) are not built. A map-only scenario is a new text map and a new SeaScenario entry.

How the AI plays it

It settles first and sails second. A ship is built when a settlement spot reachable by sea (up to five steps from its open end) is worth having, with a bonus for an island nobody has landed on, and ahead of a development card when that bonus is in play. A spot beside a village that still has cloth, or beside a tribe chip nobody has taken, is worth more (CatanAi.scenarioLure), a ship that heads for a standing fortress is worth building, and it raids and builds wonder stages whenever it can pay (CatanAi.FORT_LURE). It chooses the resource it values most from gold, always moves the robber (never the pirate) and does not sail ships it has already launched. See CatanAi.shipValue.