Sonic Mania | Plus Decomp

To discourage piracy, the developers often disable DLC features (Mighty, Ray, and Encore Mode) in official release binaries. Users who legally own the DLC must compile the project from source to enable these features. Features and Improvements

Sega has historically had a surprisingly lax relationship with the Sonic modding community, even hiring fan game creators (like Christian Whitehead himself) to work on official titles. While they have not officially endorsed the decomp, they have notably refrained from issuing DMCA takedowns, recognizing the passion of the fanbase. sonic mania plus decomp

You need – the Plus DLC is not required for code but is needed for Plus assets (Mighty, Ray, Angel Island Zone). To discourage piracy, the developers often disable DLC

The project allows the game to run on platforms not officially supported by SEGA, including various Linux distributions and the Nintendo Switch via homebrew. While they have not officially endorsed the decomp,

This project is not a standalone "free" game. It requires the original assets—specifically the Data.rsdk file—from a legally purchased copy of Sonic Mania or Sonic Mania Plus to function.