A suggestion for the visual area widget: Count the boxes for the user. So in the first box you'd write 1, the second 2, etc. Then it's easy to verify that the numbers are indeed a counting (they increase by 1) and that the calculated are indeed checks out.
I'd write the numbers in gray so they don't dominate the image.
Thanks for the feedback. There is a lot of work that still needs to be done to improve the UI for these tools, but our goal is to build a library of such visual tools for tens of relevant topics.
I'd write the numbers in gray so they don't dominate the image.