The problem
Most budgeting apps are good at the past tense — they categorize what you already spent. The question people actually carry around is forward-looking: given what's left over each month, what should I do with it, and how long until it matters? Answering that means opening a second app for investment math and a third for a debt payoff calculator, then reconciling three sets of numbers by hand.
Approach
Everything runs in the browser. No account, no bank linking, no backend — data lives in local storage and never leaves the device.
INCOME + EXPENSES ─▶ SURPLUS ─┬─▶ INVEST (compound projection)
(normalized to ├─▶ GOALS (time-to-afford)
a monthly figure) └─▶ DEBT (amortization + payoff plan)
- Budget — income and expenses at any frequency are normalized to a monthly figure. The app surfaces the numbers that actually change behavior: total subscriptions, annualized dining spend, and a 50/30/20 check. If spending tops income, it names the largest non-essentials and shows what halving each recovers.
- Invest — the surplus pre-fills a compound-growth projection with honest framing: a 4/7/10% side-by-side so the answer's sensitivity to the return assumption is never hidden. A stock lookup pulls a ticker's real last-decade return and volatility from public market data — labeled as history, not a prediction. It never recommends a security.
- Goals & debt — savings goals get a realistic target date from the surplus. Loans get full amortization from their APR: payoff date, total interest, the warning when a payment doesn't even cover interest, and an avalanche-vs-snowball payoff plan that rolls each cleared balance into the next.
What it outputs
One screen per question, all recalculating live: a surplus and savings-rate readout, a growth chart that separates contributions from interest, a goal timeline with the exact monthly amount to hit 6, 12, or 24 months, and a debt plan that shows years and dollars saved against paying only the minimums.