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Case study

Sonic Mania: a game-code decompilation for the RSDKv5 engine

Reconstructs Sonic Mania’s game code in C and builds it with the separately decompiled RSDKv5 or RSDKv5U engine for Windows, Linux, Switch and Android. Assets must come from an official Sonic Mania (Plus) release; the project adds a mod loader and can build several retail versions. Its license describes the code as mostly functionally the same as the original, not byte-matching.

Requirements and limitations

  • The repository describes itself as a complete decompilation of Sonic Mania (2017); its license says it also contains original code and that most code is expected to be functionally the same, so no byte-matching build is claimed. It adds a built-in mod loader and API and can build 1.00 (console launch), 1.03 (PC launch) and 1.06 (Plus update) variants. The reviewed commit is 15 commits after release v1.1.1 (2025-11-01).
  • It does not run without assets from an official Sonic Mania (Plus) release for Windows (Steam or Epic Games Store), Switch, PS4 or Xbox One; the Netflix Games version is not supported. By default it builds with the bundled RSDKv5 engine submodule at revision 3 (RSDKv5U) and game version 6, the last Steam release; with WITH_RSDK off it builds only the game code, and RETRO_DISABLE_PLUS is to be enabled for distribution builds.
  • Clone recursively, because GitHub’s source ZIPs omit the required submodules. CMake builds use Visual Studio with vcpkg (libtheora, libogg, GLEW, GLFW3, SDL2) on Windows, build tools with GLEW, GLFW and libtheora development packages on Linux, devkitPro packages for Switch, and the engine repository’s instructions for Android. GL builds need a user-made shader mod for videos and filters.
  • CI builds Windows x86 and x64 and Linux binaries against both the RSDKv5 and RSDKv5U configurations. The project publishes no comparison with the original binaries, and its FAQ says bugs present in official releases will mostly not be fixed. This collection did not build or run it.
  • The custom Sonic Mania Decompilation Source Code License v1 allows copying, modification and distribution only for non-commercial use, requires stating that the code is not the distributor’s, forbids distributing game assets other than unique modded ones, and binds forks to the same terms. Sega’s game and assets keep their own rights. 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/Sonic-Mania-Decompilation · Revision 9dc6994
  2. LICENSE.md GitHub · RSDKModding/Sonic-Mania-Decompilation · Revision 9dc6994
  3. .gitmodules GitHub · RSDKModding/Sonic-Mania-Decompilation · Revision 9dc6994
  4. .github/workflows/build.yml GitHub · RSDKModding/Sonic-Mania-Decompilation · Revision 9dc6994
  5. https://github.com/RSDKModding/Sonic-Mania-Decompilation/releases/tag/v1.1.1