Challenge: Perfect Run
Nobody's Perfect, and that applies on Duolingo as well as in real life. Here, we make lots of mistakes at first when we're learning a new language. I therefore suggest (personally) that after finishing a tree, one goes through all the lessons, chronologically, and attempts to do each with perfect scores 3 times in a row. If you've finished the tree, try it! How proficient are you?
Well, if you're truly native and assuming you make no typing errors, it'd be easy.
Sure for the most part, but if it is too easy you just breeze through and that's when the typos start to show... And of course there are the occasional moments when Duolingo wants some specific was of translation and does not accept other, even natural ways of saying the same thing :)
Quite hard to get completely rid of human errors on either side, though of course something like 98% success rate should be achievable if you really know what you are doing...
Good points. This would be a great way to report issues in courses and make Duolingo more accurate. 95% is a decent success rate for a perfect run.