Rendimento.
Projects compound interest with income tax and inflation already deducted, compares eleven investments under one scenario and tracks FX, crypto and B3.
The problem
Every bank simulator shows the gross figure, and gross is the one number nobody ever receives. After the regressive tax and the inflation of the period, what is left is something else — and comparing savings, CDB and Treasury bonds means putting all three under the same rule, which a spreadsheet rarely does.
What I built
A pure calculation engine, covered by tests, projects the future value or solves for the contribution a goal requires, always in present-day money. Eleven investments enter the same scenario and are ranked by net return; the app runs entirely in the browser, with no backend and no data collection.
Stack
- React 19
- TypeScript
- Vite
- Zustand
- Recharts
- Zod
- Vitest
What I learned
Stale data shown as current is worse than no data. If an API drops, each market block falls back to the last good value and labels itself delayed, instead of lying with a fresh face.