The Grothendieck method can be applied to implementing a new feature in a software system. You just refactor the existing code until the implementation of the new feature becomes trivial.

When reading code you don't really understand, that approach looks a lot like magic. I have a few code bases I try to follow, one is a large Java application, and some of the features added seemingly come out of nowhere. The commit message will just say "Add support for XYZ" and then a few lines added to seemingly random files to setup of condition and then the feature manifests itself.