I'm not familiar with the tool, but judging by this text, it should be able to repack the rsdk file:
Retrun-Sonic is a packer/unpacker for games made with The Taxman's Retro-Engine SDK (RSDK), which means, yes, that you can now
unpack the datafile of the new Sonic CD remake, modify the contents and then make a new datafile with the new contents, thereby modifying the game data.
So in my case this command prompt is not working. Also this tutorial is also not working anymore. So I downloaded rsdk extractor. I know this video tutorial is old,right? There's also another not outdated video tutorial.
I want to know one thing what happened with Sonic Mania Mod Studio why download links are no longer available and also old modding tutorials are outdated did creators of Sonic Mania changed a file structures in later updates aka Sonic Mania Plus or what? I really liked that old modding methods and I'll miss them.
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