Got Tutorials - Using Navigation View to work on Mac with Safari browser.
When run on iOS Simulator "crashes" (no error messages) when enter any number on first screen
Please advise

When run on iPhone gets to third screen ("Step 3") but display is wrong -- looks like:
Step 3 (just text no back arrow)
Step 2 (just text no back arrow)
Choose an operation
(*) Add
() Subtract
() Multiply
() Divide
Keyboard is diplayed here -- when press "Done" Keyboard disappears

But, nothing happens when touch the Calculate! (just stays on same screen)
Please advise

Also, how should I try to debug this kind of scenario in the future (works in browser, does not on device)?