You may be interested in this article: https://medium.com/@kris-nova/organic-and-mechanistic-systems-e576ac470845 https://medium.com/@kris-nova/organic-and-mec

You may be interested in this article: https://medium.com/@kris-nova/organic-and-mechanistic-systems-e576ac470845 https://medium.com/@kris-nova/organic-and-mechanistic-system... What you are dealing with is organically grown software. No one really understands it, and it's likely to be fragile. I agree with all those here that say the first thing to do is to introduce version control. You don't want to break that money machine without a way to revert. Second, introduce some lightweight form of code review, but don't tick people off. Third, if you want to do something like revise the user interface, consider adding an API to the existing organic code base, and build the new UI with that API. Generally, take that approach and avoid jamming something into the middle of the existing code that no one fully understands.