## Build & Development Commands
- Always scaffold components using React.js with functional components and Hooks (useState, useEffect).
- Tailwind CSS should be used for mobile-first responsive design.
- Prefer using Firebase Firestore for backend database and authentication.

## Testing Guidelines
- Keep simple unit tests using Jest or React Testing Library where necessary.
- Prioritize manual testing first for barcode scanning and invoice generation.

## Code Style & Guidelines
- Use modern JavaScript (ES6+).
- Do NOT use TypeScript.
- Always include clear JSDoc comments above major functions and components.
- Follow React Hooks and Context API best practices for state management.

## Documentation Guidelines
- Reference https://react.dev/learn for React related questions.
- Reference https://tailwindcss.com/docs for Tailwind related styling.
- Keep documentation lightweight, focused on business flows (scan → checkout → invoice).