This is terrific! I'm a native English speaker starting to learn Chinese. To be able to hover over the characters and see the pinyin has been nice.

One question: I'm an old school English learner in that I've done in-depth grammar study and can list tenses, parts of speech, and other things most people younger than I don't care about. Are there any web sites out there that list things like tenses, parts of speech, and grammar "rules" for Chinese? 

As an English learner, I'm trying to make connections and comparisons to facilitate my learning process, and everyone just seems to dump me in the middle of the language without the guideposts I need (hoping the analogy works).