You only give two forms- "todavia no [verb]" and "no [verb] todavia", yet a vast majority of your sentences are "no [entire sentence] todavia" as you put "yet" at the end of the sentence. But, even when you do put the word "yet" early in the sentence, you still require "no [entire sentence] todavia" as the answer, which is not even an option in the instructions above.  It makes it very frustrating as I am struggling with a recent surge in progress and trying to solidify it and work my way through A2.  Your site is wonderful, but there are a few frustrating areas :)