Expandia

Expandia is a worldgen / progression mod for Minecraft !

You spawn on a small island at 0, 0. The rest of the Overworld is open ocean. There is no continent waiting over the horizon, if you want more land, you play the game.

Each configured advancement you complete reveals one new island. Same idea in the Nether, except the sea is lava. Islands spread out in a spiral so they never overlap, with water (or lava) between them.

If you already explored that area as ocean, it still updates. The chunks are rebuilt on the fly, and chat tells you the coordinates. Press K to open the island advancements screen: what's unlocked, what's left, with search and filters.

Features

• A spawn island at (0, 0), 32 blocks radius by default. Every island uses the same size.
• Overworld: open ocean around the islands (plain ocean, no icebergs).
• Nether: same layout, lava instead of water.
• Advancement-driven. One island per listed advancement, saved per world.
• Live reveal. New islands appear without a restart, even in already generated chunks.
• Island advancements screen (default key: K).
• Islands stay compact on purpose. No vanilla structures, caves, or aquifers, the land you have is the land you have. Surface biomes still generate normally.
• Works with Terralith and other biome mods. Expandia only masks land vs ocean; it doesn't override biomes on the islands.

Multiplayer

Works on LAN and dedicated servers. The map is shared: islands belong to the world, not to each player.

• The first player to complete a listed advancement reveals that island for everyone.
• If someone else completes the same advancement later, nothing extra spawns, that island is already out.
• New land is in the world for the whole server. Anyone can sail there.
• The K screen shows world unlocks on one side, and which advancements you have done on the other.

For pack makers

Config lives in config/expandia/progression.json. Add or remove advancement ids, change the island radius, done. Datapacks can ship defaults under data/<namespace>/expandia/progression.json; the config file always wins on top.

• /expandia islands -> island counts (anyone)
• /expandia unlock <count> -> spawn extra islands (op)
• /expandia reset -> back to the spawn island (op)
• /expandia reload -> reload the config without restarting (op)

Terralith is optional. If you use it, load Expandia after it.

I mainly made it for my upcoming modpack, Expandia: Arcane & Alloy, but it's a standalone mod. Drop it in any world or pack, it doesn't depend on the rest of the pack.