@Craigrut,

I agree, and I'm kicking myself because correction was on the list of suggestions. You get an answer wrong but have no idea what to do to correct it. Correction is an important component.

The only thing I disagree with for the explanation to be in English. Bilingual explanations would be better, but honestly the earlier point we disconnect from the English crutch, the better. Perhaps beyond intermediate level the explanations should be in Chinese.