Build a React component that lets users compare the carbon footprint of two activities side by side. For example: "Driving 20 miles vs. Taking the train 20 miles".
- Two input panels.each with activity type selector and parameters
- Real-time calculation as inputs change (debounced)
- Visual bar chart comparison showing CO2 in kg
- "Did you know?" fact based on the difference (e.g., "Switching to train for this trip saves X kg CO2/year if done daily")
- Share button that generates a URL with encoded parameters
Use the calculator modules internally (don't call the API). Make it accessible (ARIA labels, keyboard navigation).