welsh duo lingo
Just a suggestion, is it possible to put in sections (or more sections, if they're already there) where you are given an English sentence and asked to translate it into Welsh? A problem I've noticed while learning languages on Duolingo is that the courses tend to give you a lot of opportunity to practice your New Language to English translation, but not so much English to New Language. But that's the part I want to improve.
Otherwise, I agree with sharkboy1100 - it's amazing being able to learn Welsh so easily. I'm learning more from Duolingo than I did from eleven years of learning it in Welsh lessons in English-medium schools in Wales.