One suggestion that I would like to make is not about the tests, but about the popups themselves. I have no idea how they work. I believe they still get stuck on IE if you click on them and don't get unstuck, but that bug may have been fixed. Then (after you've clicked on it) you can edit its contents. I am not sure what that feature is for, since after you close the popup (on Chrome, since in IE this is broken), its contents does not change. I had rather, instead of the useless editing feature, have popups split multi-character words into separate characters, as it is impossible to learn a word (in its written form) without learning the individual characters.

Alternatively, the vocabulary for a lesson could just call out the individual characters. That would avoid readers having to look that up. As the characters do not appear in the podcast on their own, that would naturally be a premium feature.