SWF Game Port Decompiler

Decompile SWF games for engine ports using FFDec/JPEXS.

Use this skill to decompile old Flash/SWF games into a porting workspace: code, assets, frame/sprite renders, tag structure, XML timeline data, and a short audit that helps rebuild the game in a modern engine.

Requirements

• JPEXS Free Flash Decompiler / FFDec installed.
• Prefer ffdec-cli.exe on Windows or ffdec/ffdec.sh elsewhere.
• Java available if running FFDec from ffdec.jar.
• Python 3.9+ for the bundled orchestration script.
• Optional: ImageMagick/ffmpeg for later contact sheets, spritesheet processing, audio conversion, or video inspection.

Safety And Scope

• Only decompile files the user owns or is authorized to port, preserve, research, or migrate.
• Treat decompiled ActionScript as reference, not clean source. Expect obfuscation, compiler artifacts, timeline-side code, generated names, and dead code.
• Never overwrite the original .swf. Write all output to a separate decompile folder.
• Do not run the SWF in Flash Player unless explicitly needed and isolated; FFDec extraction is safer than executing unknown SWFs.
• Port behavior by understanding gameplay systems, not by blindly translating every decompiled line.

Main Workflow

1. Locate FFDec:
   • Windows common path: C:\Program Files (x86)\FFDec\ffdec-cli.exe.
   • Otherwise search PATH for ffdec-cli, ffdec, or ffdec.sh.
2. Create a clean output folder named after the SWF.
3. Run the full extraction:
   • python scripts/ffdec_game_decompile.py full game.swf out/game-decompile
4. Inspect the produced folders:
   • code/actionscript for AS1/AS2/AS3 source.
   • code/pcodehex for lower-level P-code when source is missing, wrong, or obfuscated.
   • assets/images, assets/shapes_svg, assets/shapes_png, assets/sounds, assets/fonts, assets/text, assets/binary.
   • timelines/frames for rendered main timeline frames.
   • timelines/sprites for rendered movie clips/sprites.
   • structure/tags.txt, structure/movie.xml, structure/symbolClass.csv.
   • PORTING_AUDIT.md for a generated first-pass map.
5. Reconstruct scene/frame structure:
   • Use movie.xml and tags.txt to identify DefineSprite, PlaceObject, ShowFrame, DoAction, DoABC, labels, exports, and symbol classes.
   • Use rendered frame and sprite exports to understand visual state changes that are hard to infer from code alone.
6. Build a porting map:
   • Identify entry points: document class, frame scripts, button actions, exported symbols, preloaders.
   • Identify systems: input, physics/movement, collision, enemy/projectile spawns, score/state, inventory, audio, level loading.
   • Pair assets with code references and symbol IDs.
   • Separate reusable engine assets from timeline-only artifacts.
7. For modern engine migration:
   • Prefer recreating gameplay architecture natively.
   • Use extracted images/audio/vector art as assets when licensing allows.
   • Use frame/sprite renders as visual reference or temporary placeholders.
   • Translate coordinates and timing carefully: Flash uses stage/timeline/frame-rate assumptions that rarely map 1:1 to modern engine scenes.

Useful FFDec CLI Commands

The helper script wraps these, but know the underlying calls:

• Export ActionScript:
  • ffdec-cli -format script:as -export script out/code/actionscript game.swf
• Export P-code with hex:
  • ffdec-cli -format script:pcodehex -export script out/code/pcodehex game.swf
• Export visual/audio assets:
  • ffdec-cli -format image:png_gif_jpeg_alpha,shape:svg,sound:mp3_wav,text:plain -export image,shape,sound,text out/assets game.swf
• Export timeline renders:
  • ffdec-cli -format frame:png,sprite:png,button:png -export frame,sprite,button out/timelines game.swf
• Dump tags:
  • ffdec-cli -dumpSWF game.swf > out/structure/tags.txt
• Export XML structure with externalized scripts/images/sounds:
  • ffdec-cli -swf2xml -external all game.swf out/structure/movie.xml

Porting Heuristics

• If source and P-code disagree, trust P-code/tag structure more than decompiled high-level source.
• Timeline code may be gameplay code. Search decompiled code for onEnterFrame, addEventListener, ENTER_FRAME, gotoAndStop, gotoAndPlay, attachMovie, duplicateMovieClip, hitTest, _root, _global, stage, and exported class names.
• For AS2 games, expect frame scripts and dynamic movie clip attachment. For AS3 games, expect document classes, package directories, DoABC, and event listeners.
• Use symbolClass.csv to connect class names to character IDs.
• Use rendered frames/sprites to verify animations, frame counts, origin assumptions, and sprite nesting.
• Build a small behavior table before coding the port: original symbol/class, role, extracted assets, update loop, collision/input hooks, new engine node/component.

Output Contract

When finishing a decompile-for-porting pass, report:

• SWF path and output folder.
• FFDec command/source used.
• Extracted categories and notable counts.
• Whether ActionScript, P-code, XML structure, frame renders, and sprite renders were produced.
• Important entry points and obvious game systems found.
• Gaps: failed exports, obfuscation, missing external assets, encrypted/protected SWF, or unsupported features.
• Suggested next porting step.