[nemetroid]

I agree. I used to work on a project where everyone involved in the initial design had left the company, and documentation was spotty. The major issues I had working with the code were all related to not understanding the underlying design choices, e.g. why a certain model was chosen over another or how a certain abstraction was intended to be extended with new functionality.

Stuff that can be formalized in a systematic manner is usually stuff you can figure out on your own in a text editor or IDE.

[lllr_finger]

We've been capturing those decisions in ADRs (https://www.thoughtworks.com/radar/techniques/lightweight-ar...) for the past year or so, and they've been incredibly helpful even for those involved in the original decisions that want to revisit the rationale - I can only imagine how helpful they'd be in a situation like yours.