# Geek Calculator

A single-file, offline-capable calculator with a terminal-like interface. Features basic arithmetic operations, RPN mode, keyboard-first operation, and a "geek vibe" aesthetic.

## Features

- Basic arithmetic operations (+, -, ×, ÷)
- Parentheses support for complex expressions
- Percentage calculations
- Positive/negative toggle (±)
- RPN (Reverse Polish Notation) mode
- Full keyboard operation
- Command palette (access with @ key)
- Calculation history with re-run capability
- Terminal-themed UI with ASCII banner
- Full offline capability
- Keyboard accessibility (ARIA roles, focus indicators)

## Usage

### Basic Operations
- Click buttons or use keyboard: `+`, `-`, `*`, `/`, `=` 
- Use `Enter` to evaluate expressions
- Use `Escape` to clear current input
- Use `Backspace` to delete last character

### RPN Mode
- Toggle RPN mode with the RPN button
- Enter numbers followed by operators
- Example: To calculate `4 + 6`, enter: `4 ENTER 6 +`

### Keyboard Controls
- Numbers: `0-9`
- Operators: `+`, `-`, `*`, `/`
- Equals: `Enter` or `=`
- Clear: `Escape` or `C`
- Decimal: `.`
- Backspace: `Backspace`
- RPN Enter: `Enter` (in RPN mode)
- Toggle RPN: `R`
- Command Palette: `@`
- History Navigation: `↑` and `↓`
- Help: `?`

### Command Palette
- Press `@` to open the command palette
- Type commands like "clear", "history", "theme", etc.

## Offline Capability
The calculator works completely offline. The first time you load it, it will cache all necessary files using a service worker.

## Technical Details

- Pure HTML/CSS/JavaScript (no external dependencies)
- Total payload < 50KB
- Uses ES6 modules for code organization
- Service worker for offline functionality
- LocalStorage for calculation history
- Accessible with full keyboard navigation and ARIA roles

## Development

To run tests:
1. Open `tests/index.html` in your browser
2. Tests will run automatically

## Architecture

- `calculator.js`: Core calculator logic
- `rpn-calculator.js`: RPN calculator implementation  
- `ui.js`: User interface interactions
- `state.js`: Application state management
- `utils.js`: Utility functions
- `styles.css`: All styling (dark theme, ASCII art, responsive)
- `service-worker.js`: Offline functionality
- `manifest.webmanifest`: PWA features

## Size Budget
The entire application is designed to stay under 50KB total payload.