I've mastered all the Spanish skills at Duo. I'll stick around and maybe do some translations or answer a few questions from time to time, but i'm really looking forward to getting Portuguese on this site. I would have liked to see some explanations of different constructs, idioms, etc. rather than simply taking tests. I sent some feedback on a number of answers that were correct but marked wrong and received a reply only on one or two. There is a lot that needs to be done to make this site really viable as a long term learning tool.