Neat project, although selecting cells often does not work. (I assume that's because it's in alpha.)

This line, though:

> is lightweight: ~2000 lines of source code (excluding libraries)

I feel like that's a very different meaning of "lightweight" than I normally think of. I guess you're considering it from the perspective of a developer who works on it. As a user, however, the browser downloads 1.4MB of javascript, which is quite large, I'd say.