Duolingo must be a New Zealander, using words like "Awesome" and "Pretty Sweet" when you finish your lesson. I'm a Kiwi, so it makes me feel right at home!
LOL, not sure if those expressions are strictly Kiwi. I hear them being used here as well, particularly by younger people. I've noticed that Duolingo often uses American spellings for English words in its examples, however, it also accepts the British (Canadian/Aussie/Kiwi) spellings when you make a response. Also, there seems to be a few expressions that seem to be very British that I recognize but I wonder if our US friends do.
In my nationalistic pride, I wanted to believe that they are unique to this tiny island and its 4 million inhabitants. But it sounds like you are a Brit living in the States, and with this exposure you would know better than me. But I bet you didn't know 'ka pai, eh cuz' - Alex is from Pukekohe.
You're right, I don't know 'ka pai' although since my REAL cousin lived in NZ for a number of years, I could probably find out. The 'net' says it means "well done". Until I looked it up, I had no idea what Pukekohe was either. But you're not even half correct about me being a Brit living in the US. My father was from 'the Aulde Sod' (which Americans likely wouldn't understand) and my mother descended from the Emerald Isle, but I was born in Canada and worked in the US for years. So I was "multilingual" after a fashion. When I did work in the US, I was often called upon to translate Britspeak for the Yanks who had no idea what some of our English colleagues were saying, but to me it was everyday conversation.
Duolingo: educating the world about unimportant NZ towns, one Canadian at a time. Ka pai is probably close enough to 'sweet as' to be used as its equivalent, at least to us pakeha (NZ european). Each country, place and even social level has its own subculture. I understand this is the same for Austrians\Sweedes? Does this course teach a pure Germany-German? Perhaps the differences are too subtle to be worried about on this basic level.