dapkniht/Bmi-Calculator-Flutter — reverse-engineered prompt

Turn this starter Flutter project into a simple BMI calculator app that feels polished and is easy for a normal person to use.

I want the user to enter their height and weight, choose common units if that makes sense, tap a calculate button, and immediately see their BMI number with a clear label like underweight, healthy weight, overweight, or obese. Add a short plain English explanation of what the result means, but keep it friendly and not medical sounding.

Please make the screen clean and modern, with good spacing, readable text, and buttons that work well on a phone. Handle empty or weird inputs with helpful messages instead of crashing. If there are existing placeholder Flutter files, replace them with the real app code and keep the project runnable.

Use Flutter best practices, but don’t overcomplicate it. Look up current Flutter docs online if you need to.