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Case study

RSDKv4 Decompilation: Retro Engine v4 and the Sonic 1 & 2 (2013) menus

Decompiles Retro Engine (RSDK) v4, the engine behind Sonic the Hedgehog and Sonic the Hedgehog 2 (2013), together with the games’ natively coded menus, and builds it for Windows, Linux and Android. The engine runs the game scripts contained in the official releases’ data files, which users must supply. The project adds a script compiler, a mod loader and an experimental online mode for Sonic 2’s 2P VS; it is the predecessor of the same group’s RSDKv5 decompilation.

Requirements and limitations

  • Reviewed at the 2026-09-06 main head, 13 commits after release 1.3.3 (2025-11-02). README calls it a complete decompilation of Retro Engine v4 and the menus from Sonic 1 and 2 (2013); the licence says most code is meant to be functionally the same as the specified RSDK version, so no byte-matching build is claimed. RETRO_REVISION defaults to 3 (Origins), and RETRO_ORIGINAL_CODE removes the project’s changes but, per CMake, cannot build a playable game.
  • It will not run without assets from an official release of Sonic 1 or Sonic 2: README names Sonic Origins on Steam, the Epic Games Store and Switch, and the now-delisted iOS and Android releases. The FAQ notes that Origins data files are packed as RSDKv5 datapacks and lack the games’ music and sound effects, and that release builds and autobuilds disable the DLC and block Origins’ Amy; the repository ships no game data.
  • Clone recursively, because GitHub’s source ZIPs omit the stb, tinyxml2, asio and Flatpak submodules. CMake 3.10+ builds use Visual Studio with vcpkg (GLEW, SDL2, libogg, libvorbis) on Windows, the listed GLEW, SDL2 and Ogg/Vorbis packages on Linux, and a separate Android guide; Xcode, UWP and Flatpak projects are included, while Vita, Switch, 3DS and WebAssembly ports are unofficial forks. Sonic 2’s online 2P VS needs a Python 3.8+ server that README calls a very unstable proof of concept.
  • CI builds Windows x86 and x64, Android and Linux binaries with the Plus DLC disabled; it runs no tests, and the project publishes no comparison with the original engine binaries. The FAQ says bugs present in official releases will mostly not be fixed. This collection did not build or run it.
  • The custom RSDKv3/v4 Decompilation Source Code License v2 requires distributed prebuilt executables to default to DLC off, forbids commercial use and distributing game assets other than unique modded ones, requires crediting the original RSDK author Christian “Taxman” Whitehead and the decompilation authors Rubberduckycooly and st×tic, and binds forks to the same terms. The reviewed sources establish no AI or REA use.

About this entry

Type
Case study
Category
Independent reconstruction cases
Relationship
Independent reconstruction project
Targets
Game

Sources reviewed

The description was reviewed against primary sources. This does not establish runtime testing, security auditing or verified compatibility.

Primary sources

  1. README.md GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  2. FAQ.md GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  3. LICENSE.md GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  4. CMakeLists.txt GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  5. .gitmodules GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  6. RSDKv4/NativeObjects GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  7. .github/workflows/build.yml GitHub · RSDKModding/RSDKv4-Decompilation · Revision a7f5195
  8. https://github.com/RSDKModding/RSDKv4-Decompilation/releases/tag/1.3.3