Expense Tracker

# Expense Tracker PRD

## Overview
Build a personal finance tracker that lets users log income and expenses, categorize transactions, visualize spending with charts, and set budget goals per category.

## Requirements
- Add transactions with amount, description, category, date, and type (income/expense)
- Category management with customizable icons and colors
- Monthly summary dashboard showing total income, expenses, and net balance
- Pie chart showing spending breakdown by category
- Line chart showing spending trends over time
- Budget limits per category with visual progress bar
- Filter transactions by date range, category, and type
- Edit and delete existing transactions
- Recurring transactions (daily, weekly, monthly)
- Export transactions to CSV
- Running balance display
- Search transactions by description
- Monthly comparison view (this month vs last month)
- Persist all data to localStorage
- Responsive design for mobile and desktop

## Tech Stack
- JavaScript or any frontend framework
- Chart library allowed (Chart.js, Recharts, etc.)
- localStorage for persistence

## Scoring Criteria
- **Functional (40%)**: Transaction CRUD works, charts render correctly, budget tracking works
- **Quality (20%)**: Clean code, accurate calculations, smooth interactions
- **Fidelity (25%)**: All features present including CSV export, recurring transactions, and comparisons
- **Speed (15%)**: Time bonus