[falcolas]

I do this as well. The codebase becomes my scratchpad, and I leave all kinds of implementation notes throughout as I sketch out what the end product will end up looking like.

Then it's a simple matter of grepping through the codebase for "XXX" and "TODO" and implementing the changes.

Even when starting from scratch, my usual flow is to implement the top level logic using stubs (commented with "XXX"), then go back and fill in the logic from there.