The problem
I wrote five mods for Brotato, the arena roguelite: two new items (Doom Pearl grants an extra shop ban token, Void Pearl curses an item of your choice), an automatic save system, a weapon win tracker and a jukebox for your own music. The 1.2 update, Primal Dread, changed the game underneath them. Saving a run crashed, the shop crashed on open, and the way the mods registered items no longer did anything.
What I built
A full port of all five mods to Brotato 1.2 and its mod loader 6.3. I set myself a strict rule: no shims around the old code. Each mod now uses the game's own mechanism for the job, as if the game's developers had written it. The pearls register as item sets exactly like the game's official updates, the Void Pearl only when the Abyssal Terrors DLC is owned; saves reuse the game's own run state and save loader; weapon records reuse the game's own score type and live next to each save profile; menu pages follow the game's own Mods page pattern.
Technical challenges
- Mapping the update. Before touching a mod I wrote a function-level diff of every game script the mods extend, between the old version and 1.2, with a ranked list of risks.
- Playing nicely with other mods. Several mods extend the same game scripts, so every override calls the original and targets the narrowest function available.
- No compiler to lean on. Every path, inherited script, game function and signal the mods use was checked against the 1.2 scripts, with file and line references in a report per mod.
- Fixing what was there. The port also fixed bugs that predated it, such as a WAV parser that misread several formats and a Void Pearl curse that accepted items it shouldn't.
Outcome
All five mods are on version 1.1 and declare compatibility with Brotato 1.2.0.0 and 1.2.0.1. A ten-step in-game test plan, solo and co-op, with and without the DLCs, covers the release.