its illegal, to get the source for yourself use DnSpy and uUnityRipper
i mean-
i also wanted to make something similar, infact, at one point i tried making like … A karlson fangame that has new custom levels, the issue is that I never found the source code, i never managed to use DnSpy & utiny ripper to get the unity project + source code, which is sad ):
I kinda wish i have the source code just to mess with it, but i understand why it isn’t publicly shared