"Double-entry" sounds like CPA territory, but the idea fits on a napkin: money never appears or vanishes — it moves.

Buy rent with cash? Cash went down, expense went up. Invoice a client? They owe you more, you've earned revenue. Every record has two sides that must agree, which is why the books can't quietly lie.

NapkinLedger runs true double-entry under a friendly surface. You fill one short form; the engine writes balanced ledger lines behind it. You get accountant-grade integrity without accountant-grade vocabulary.