ajax.googleapis.com/google hosted files may failed to load, then leave duolingo unusable
ajax.googleapis.com and many parts of google's service is blocked in mainland China, then many fuctions of duolingo become unusable. I suggest at least set an option for users let them decide where to load the js files (like reddit has a option: load core JS libraries from reddit servers)
I have read many similar reports from duolingo's chinese users in only one month: https://www.duolingo.com/comment/4653927 https://www.duolingo.com/comment/4653927 https://www.duolingo.com/comment/4245334 https://www.duolingo.com/comment/4161446 https://www.duolingo.com/comment/4125272 https://www.duolingo.com/comment/4017456 and counting... I'm very frustrated about duolingo keeping ignoring our feedback, I even reported the problem months before!