Congrats on finishing the challenge!

In the future make sure you draw big boxes, do about 5-6 per page and make sure they take up the page. This will help you improve faster.

I also suggest varying the shape of your boxes more, try to construct different Y shapes than you are used to.

I think your inner corners are pretty good but this ordering: can help you improve it more.

This exercise can now be incorporated into your regular warm-ups.