I see a lot about source codes being leaked and I’m wondering how it that you could make something like an exact replica of Super Mario Bros without the source code or how you can’t take the finished product and run it back through the compilation software?
Others have explained that decompiling is a thing.
I mainly work in Java where (due to the way Java bytecode works) decompiled code is actually very close to the original source code.
Most games are written in low level languages like C++ where that is not the case, variable and function names are lost during compilation.