Data packs

A data pack is a mod's data/ folder. It mirrors the game's own data folder (data/ next to the game): a file at the same place replaces the game's, and a file the game does not have is added.

mods/
  night-menu/
    mod.toml
    data/
      art/main/31000.png      the Game Start picture
      art2x/main/31000.png    its 2x copy

Which file wins

When the game looks for a file it tries the packs from the mod lowest in the Options list up, then its own folder. So the last mod in the list wins where two replace the same file.

Pictures

Pictures are PNGs in art/<set>/<id>.png, where the set is the image file they came from (main, universe, planets, ships, combat, empire, infra, surface, tech, advisors) and the id is the picture's number in it.

• They are 8-bit indexed. A picture is drawn with the palette of the screen showing it, not its own, so a replacement must use the same palette indices as the picture it replaces. The easiest way is to start from the game's own picture and change only its indices, as the Night Menu sample does.
• 2x copies. Upscaled art sits in art2x/ at the same place. The game uses a 2x copy only from the same pack as the 1x picture (or a later one). A pack that replaces a 1x picture without a 2x copy gets its own picture scaled up, never the game's old 2x one.

Other files

Sounds, music and the game's tables are under data/original/ as the game's own files. Fonts are under data/fonts/. Replacing them works the same way, file for file.

Never ship the game's own files

A pack made by changing the game's art holds the game's art, which you may not share. The Night Menu sample builds its picture at install time from the player's own game data instead: samples/NightMenu is a small program that reads the imported picture and writes the pack.