Tried the Japanese one... Can I suggest you stick to the hiragana and katakana syllabaries? You've thrown a couple kanji in there and it's confusing for some of them because you want the kanji form, but others you want straight hiragana... With no rhyme or reason for it.

I also just tried a French one (not the one you linked) and the hints to the side were less than helpful. I guess that's to be expected from a user-generated list. I think I'm also not used to listening to French, and that didn't help... Couldn't really hear what was being said. Again, that could just be my ears, though.

All-in-all, I think it'll be great learning tool... But I thought I'd bring the above to your attention.