http://www.skritter.com/forum/topic?id=69162157&comments=5 - I've already made some proposal about sentence system
Here is another one that might be useful as well: it is very very useful that the characters and words are pronounced. How about making the example sentences soundable with a button click? This way we would learn to speak the whole phrases. Those like 世界上有七大洲 might be very useful.
What would you tell guys?