# Project rules: invoice generator

## What we are building
A one-page web app where a freelancer fills in their details, the client, line items, tax and notes,
sees a live invoice preview and downloads a clean PDF. Data stays in the browser (localStorage). No backend.

## Stack
- Next.js (App Router) + TypeScript + Tailwind CSS
- @react-pdf/renderer for the PDF
- zod for the invoice shape

## Rules
- Money is stored in integer cents. Never use floats for totals.
- One source of truth: lib/invoice.ts holds the type, the zod schema and calcTotals(). UI and PDF both use it.
- Format money with Intl.NumberFormat using the chosen currency.
- Everything must work offline after the first load and on a phone.