Tyrian mods: ships, weapons, enemies and levels

The weapons, ships, enemies and sprites a mod creates are named by their author, and the original content it copies or changes is cited by its name too, such as "base": "Vulcan Cannon". The engine assigns every internal slot itself: you never pick an ID number, and two mods never fight over one.

my_mod/
  mod.json              required: "format_version": 1 and "name"
  README.md             optional: shown in Setup → Mods (1 KiB at most)
  levels/ep1_09.json    optional: events of a level
  sprites/shots/*.png   optional: images, cited by their file name

A real mod.json

This is the Alien Pack reference example, comments removed. It is not in the game package: it lives in rewrite/mods/_retired/alien_pack/ of the repository. It adds a ship and four weapons copied from original ones, tints every PNG of the mod green, and sets the starting loadout of a new game:

{
  "$schema": "../../mod.schema.json",
  "format_version": 1,
  "name":        "Alien Pack",
  "author":      "OpenTyrian2000 Team",
  "version":     "3.0",
  "description": "Green alien fleet — 4 stock weapons re-skinned via engine tint.",
  "tint":        "green",
  "enabled":     false,
  "ships": [
    { "name": "Xeno Vanguard", "base": "Gencore II", "ship_sprite": "xeno_vanguard", "always_available": true }
  ],
  "weapons": [
    { "name": "Alien Vulcan Cannon", "base": "Vulcan Cannon",          "always_available": true },
    { "name": "Alien Mega Cannon",   "base": "Mega Cannon",            "always_available": true },
    { "name": "Alien Bio Spreader",  "base": "Sonic Wave",             "always_available": true },
    { "name": "Alien Guided Orbs",   "base": "Heavy Missile Launcher", "always_available": true }
  ],
  "starter": {
    "ship":         "Xeno Vanguard",
    "front_weapon": "Alien Vulcan Cannon",
    "rear_weapon":  "Alien Guided Orbs"
  }
}

Next to it, the mod's sprites/ folder holds the ship image (sprites/ships/xeno_vanguard.png), shop icons and shots; "tint" recolours all of them when the mod loads. "$schema" is optional: it points your editor at the published JSON schema for completion and live errors. Every unknown key is reported as an error, so a typo never goes unnoticed.

The repository includes a level editor built into the Godot editor. Its Tyrian dock lets you pick a start row on the level map, Add an enemy here, Export to the mod, Build the .zip package to share, and Play from here, which starts the level fast-forwarded to the row you chose, so you can test an encounter in seconds.

The editor works from the source code: you build the game first (see docs/build.md), then open the Godot project. You do not need it to make a mod: level events can also be written by hand in levels/epN_NN.json. This example, from the modding guide, adds two enemies to the first level of episode 1:

{ "episode": 1, "lvl_file_num": 9,
  "add_events": [ { "time": 300, "spawn": "my_drone", "x": 130 },
                  { "time": 300, "spawn": "tech_corridor_32", "x": "random", "link": 3 } ] }

add_events inserts events into the original list, events replaces it, and random_enemies replaces the level's random enemies. time is the scroll position shown by the editor. Every event type is listed on the Level events page.