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RPG Maker ​

Status: Planned — No implementation started. Two very different versions exist.

RPG Maker VX Ace (and earlier) ​

Format ​

RPG Maker VX Ace stores game data in a proprietary binary format:

  • Scripts.rvdata2 — all Ruby/RGSS3 scripts, Marshal-serialized array of [id, name, zlib(source)]
  • *.rvdata2 — actors, classes, skills, items, weapons, armors, enemies, troops, states, animations, tilesets, commonevents, system, areas, maps (Marshal-serialized)
  • Map files — MapXXX.rvdata2 — room data with tile layers and event lists
  • Game.exe — bundled RGSS (Ruby Game Scripting System) runtime, not user code
  • Audio/, Graphics/, Fonts/ — asset directories

RGSS3 (VX Ace) / RGSS2 (VX) / RGSS (XP) are wrappers around Ruby with game-specific extensions for sprites, windows, audio, and input.

Lifting Strategy ​

Full recompilation (Tier 2).

  1. Extract Ruby source from Scripts.rvdata2 (decompress each entry with zlib)
  2. Parse Ruby source — well-documented language with parser gems (RubyParser, Parser gem)
  3. Convert to IR — Ruby is dynamically typed; type recovery needed
  4. Identify RGSS API boundaries

What Needs Building (VX Ace) ​

  • [ ] Scripts.rvdata2 extractor (Ruby Marshal format parser)
  • [ ] Map/event data extractor (*.rvdata2 for event commands)
  • [ ] Ruby AST → IR lowering (significant: Ruby closures, blocks, modules, mixins)
  • [ ] RGSS3 replacement runtime:
    • [ ] Sprite — bitmap + transform + viewport
    • [ ] Window / Window_Base / Window_Command — the standard menu/dialogue system
    • [ ] Viewport — z-ordered rendering layers
    • [ ] Bitmap — software raster (fill, blt, draw_text, etc.)
    • [ ] Font — typeface selection
    • [ ] Input — key polling (RPG Maker uses a fixed key map)
    • [ ] Audio — BGM/BGS/ME/SE playback
    • [ ] Graphics — frame timing, transition effects, freeze/transition
    • [ ] RPG::* data classes (auto-generated from Marshal data)

Known Challenges ​

  • Ruby complexity — Blocks, procs, lambdas, method_missing, eval, require make full static analysis hard. Most game code is straightforward but the default scripts use advanced patterns.
  • Default scripts — A large portion of the game is built-in RGSS "default scripts" (Scene_Map, Scene_Battle, Game_Player, etc.). These can be recognized and replaced wholesale with reimplementations.
  • Battle system plugins — VX Ace games often use community plugins (Yanfly, Fallen Angel, etc.) that heavily monkey-patch the default scripts. These require case-by-case handling.

RPG Maker MV / MZ ​

Format ​

MV and MZ are fundamentally JavaScript-based, already targeting the browser:

  • js/rpg_*.js — bundled engine source (obfuscated in some distributions)
  • data/*.json — all game data: actors, maps, events, skills, items, etc.
  • js/plugins.js — plugin loading manifest
  • js/plugins/ — community plugins (JavaScript)
  • audio/, img/, fonts/ — assets

Map events are JSON arrays of command lists. The event command format is well-documented (integer command codes with parameter arrays).

Lifting Strategy ​

Patch-in-place + event compilation (Tier 2, partial).

Since the engine already runs in JavaScript, the most practical approach is:

  1. Compile event scripts — JSON event command lists → TypeScript functions
  2. Optimize the engine — tree-shake unused features, replace Pixi.js calls with direct canvas
  3. Inject plugins — compile and bundle community plugins alongside generated code

Full decompilation of the engine JavaScript itself is lower value since it already targets the web.

What Needs Building (MV/MZ) ​

  • [ ] JSON event command compiler — map each command code to IR or direct TypeScript emit
    • Movement commands: move route, change direction, transfer
    • Message commands: show message, show choices, input number, select item
    • Control commands: switches, variables, self switches, conditions, loops, labels
    • Audio/video commands: BGM/BGS/ME/SE, video playback
    • System commands: battle processing, shop processing, name input, menu, save, game over
    • Character commands: show/erase/rotate/change graphic, animation, movement
    • Picture commands: show/move/rotate/tint/erase picture
    • Screen commands: fadeout/fadein, flash/shake/tint screen, weather
  • [ ] Data extractor — JSON → typed data classes for actors, items, skills, etc.
  • [ ] Plugin compatibility shim — maintain PluginManager API so existing community plugins work

References ​