Looks great and I thinks it’s a nice way to review vocab I learned some years ago now that I will be in Japan for vacation. Thanks!
However, it would be great if it was easier to select multiple vocabulary sets at once. Right now, I have to minimize many sets to get to let’s say set 20 and then select a maybe 20 to 25. That’s a lot of clicking here I would say. Maybe include a button that’s like select all sets of one level.
A second thing, I haven’t found is furigana or some pronunciation hint when doing the vocabulary test exercises. I know the meaning of the most of the words but it would be great to see also the pronunciation (maybe after clicking the right answer? Or as a tool tip). Or include a practicing mode for default word -> hiragana or something like that.