Thanks, and I completely agree with the criticism. I had intended to add groups, but didn't manage to spend anywhere near the amount of time I wanted on this, due to spending most of the weekend being ill. If you grab the downloadable version, you can check out the different categories, which was the first step towards adding groups.
I was wondering how to compare the amounts better, but hadn't even considered letting you carry the blocks. I'll have to implement that when I come back to this. I've been meaning to put in the rest of the data from the original comic, so that'll be an easy extra feature I can add. Cheers!