[katspaugh]

I built a similar thing a while back: https://github.com/katspaugh/interlinear.io

Useful when you're at a very low level of a language. Past B1 or so, it's mostly looking up individual words.

[sieve]

This is nice! Have been building something similar for Sanskrit (links in my other comment).

And yes, this is not helpful beyond a point. But most people never reach that point. So, any help is useful.