First, print it all out, in one big long piece, use tape if you have to... so it's all on a single large piece of paper... mark it up with pencil, pen, etc. Yo

First, print it all out, in one big long piece, use tape if you have to... so it's all on a single large piece of paper... mark it up with pencil, pen, etc. You have to be able to physically navigate something like that if you are to have any hope of sorting it all out. Next... some things will be poorly named, or just wrong. Fix those. Remove all dead code, and comments. They're in your GIT repo if you need them back (plus the original listing you marked up!) Find and mark up ALL side effects. Nothing outside the module should break if it were run with the same arguments twice. If that's not the case... it's an IO procedure in disguise.