# Qwen Code Instructions: Geek Calculator

## Project Overview
Calculator application with standard and RPN modes, keyboard-first operation, and terminal-like UI aesthetic. Built with vanilla HTML/CSS/JS with zero dependencies and <50KB total payload.

## Key Technologies
- HTML5, CSS3, JavaScript ES6+
- Service Workers for offline capability
- LocalStorage for history persistence
- ES6 Modules for code organization
- Custom test harness (no dependencies)

## File Structure
```
index.html          # Main application file
styles.css          # Dark terminal theme, responsive layout
app.js              # Main application logic with modules:
  ├── calculator.js    # Core calculation logic
  ├── rpn-calculator.js # RPN calculator implementation
  ├── ui.js           # User interface interactions
  ├── state.js        # Application state management
  └── utils.js        # Utility functions
service-worker.js   # Offline functionality
manifest.webmanifest # PWA capabilities
tests/              # Test directory
```

## Implementation Notes
- Keep bundle size under 50KB
- Full keyboard navigation required
- ARIA roles and accessibility features
- ASCII banner in <pre> tag
- Blinking cursor effect
- Easter eggs for fun
- RPN stack data structure
- Calculation history with re-run capability
- Command palette accessible with "@"

## Testing
- Unit tests for core arithmetic operations
- Unit tests for RPN stack operations
- Integration tests for UI interactions
- Accessibility compliance tests
- Performance tests to ensure <100ms operations

## Recent Changes
- 001-build-a-single: Added HTML5, CSS3, JavaScript ES6+ (vanilla, no build step) + None (pure HTML/CSS/JS, zero dependencies as per constitution)
- 001-build-a-single: Initial calculator implementation with standard and RPN modes
- 001-build-a-single: Keyboard-first operation with command palette