mā ma qí mǎ, mǎ màn, mā ma mà mǎ

That's a legitimate sentence, and there's only the slightest intonation difference between the different words.

This to me is why Mandarin is hard. Not the writing, not the history of the language and not the 'construction of words'.

It's the extremely subtle differences in tonality which makes it madness for a westerner (Swedish born here) to try and comprehend, and even worse to try and speak.