I'm careful to separate the design of how a thing works (theory of operation) vs the structure of its implementation. Of course there are parallels, but I would

I'm careful to separate the design of how a thing works (theory of operation) vs the structure of its implementation. Of course there are parallels, but I would treat the latter more coarsely and malleable. Give importance to the shapes/interconnectedness of the data and the processing/flow. Avoid focusing on code structure except in broad terms and don't make abstractions up-front. Prefer flatter call hierarchies (or loosely-coupled objects), avoid early/superficial 'refactoring' unless certain that it's a one-time, one-way meaningful factoring.