"Beginners and experts should see the same numbers. Only the amount of explanation changes."
The default is quiet
Keep opens in Simple mode: the restrained, low-noise surface with just the essentials. For anyone who wants more, there's Verbose mode — but here's the crucial design decision. Verbose is not a second UI, a power-user dashboard, or a different set of features. It's a semantic help layer over the exact same product: every visible component gains a plain-language definition, an explanation of what it does, and why an action matters. The stored mode changes explanation density only. It never changes a single calculation or a single stored value.
Why 'one calculation path' is the whole point
The tempting way to build a beginner mode and an expert mode is two code paths — a simplified computation for novices, the "real" one for pros. That's a trap that guarantees drift: the two paths diverge, a bug fix lands in one and not the other, and eventually Simple and Verbose disagree about what the portfolio is worth. Keep forbids this. There is one calculation path and one mutation path. Simple and Verbose are two views of identical numbers. A beginner and an expert looking at the same portfolio see the same total, down to the cent — one of them just also sees a sentence explaining what "cost basis" means.
Progressive disclosure done honestly
This is progressive disclosure with integrity. Simple mode isn't lying by omission — it's showing the true numbers with less commentary. Verbose mode isn't unlocking hidden data — it's adding definitions around the same data. Nobody is protected from the truth of their own portfolio in Simple mode, and nobody gets secret extra numbers in Verbose. The information is constant; only the scaffolding around it flexes to match how much the reader wants explained.