TESSERA4X

A mod gives the game's units, buildings, wonders, technologies, civilizations and terrain new names and new numbers, and can set the age a game begins in and switch off the victories that end in a wonder — a modern war, say. It is one JSON file. Write it by hand, or have an AI assistant write it for you, then play it from the game's New game screen.

Ready-made mods, each a click away from a game, are collected at github.com/ekorbia/tessera4x-mods.

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Have an assistant write it

1. In the game, open New game, press Mods, and press Copy the brief for AI — or copy the brief from here.
2. Paste it into Claude, ChatGPT or any other assistant, and say what you want: “archers that terrify, walls that cost a fortune”.
3. Paste its answer into the game. If anything doesn’t pass, press Copy errors for your assistant and paste those back.
4. Before you play it, press Test it in the Balance Lab: the machine plays the same worlds by the game’s own rules and by yours, and sets the results side by side — who wins, what gets built, which wonders rise.

The shape

A mod is one JSON object. format and name are required; after them come the sections, each naming entries by id and listing only the fields it changes. Everything a mod leaves out keeps the game’s value.

{
        "format": "tessera4x-mod/1",
        "name": "Bronze Rush",
        "author": "Tessera4X",
        "description": "Spears early and cheap, walls dear: the ancient world gets rougher.",
        "units": {
          "spearman": {
            "name": "Hoplite",
            "strength": 13,
            "cost": 45
          },
          "warrior": {
            "moves": 3
          }
        },
        "buildings": {
          "walls": {
            "cost": 90
          },
          "granary": {
            "yields": {
              "food": 3
            }
          }
        }
      }

How the game begins and ends

Two more keys, both optional, set the game itself rather than any one thing in it.

What a mod keeps

• Names and numbers only. A mod renames and retunes what the game has; it can’t add a unit, a building or an ability.
• What a thing is stays what it is. A few fields mark a kind — a Settler has no strength, a Warrior no range, a Granary no defence — and a mod can’t give them to a thing that has none, so it never turns a worker into a soldier or a market into a wall. Every other value, zeros included, can be set anywhere within its bounds: the tables below list exactly the fields each entry takes.
• Blurbs keep up. A blurb a mod leaves alone keeps the game’s wording with the mod’s numbers and names written in: a Granary given 3 food says “+3 food”, and a renamed Library is renamed in every blurb that names it. A blurb a mod writes is shown as written — so a new one should keep what the old one says that the mod doesn’t change. No rewrite can keep a claim true, though: when a mod’s numbers make one untrue — “the fastest”, “pays for itself” — the mod should write that blurb anew.
• Every number has bounds, listed below. The game checks a mod before it is used and names every problem by its exact place.
• Costs are at Standard speed; the faster speeds scale them down as they do the game’s own.
• The Daily and the challenges are always played by the game’s own rules, and a game under a mod counts for nothing in Your stats.
• A mod travels with its game: in its saves, and in the link its Share sends when the mod is small enough to fit.

For an editor or an assistant that reads one, there is a JSON Schema; the format is tessera4x-mod/1.

Units "units"

Buildings "buildings"

Wonders "wonders"

Technologies "techs"

Civilizations "civs"

Terrain "terrain"

Features "features"