Alrighty! So I can see that you didn't end up using an ellipse guide - most students at this stage really suffer from that choice, but all things considered you still managed fairly well. I won't be addressing any of the issues that would come from ellipses not being perfect, but your freehanded ellipses certainly are further along than most students at this stage. Ellipses are just... hard. Really, really hard.

So! Starting with the structural aspect of the challenge, you've done quite well. You've captured the curving profile of the wheel, which helps to convey a sense that the tire itself is inflated, allowing the wheel to drop to the ground with a bounce, rather than a heavy thunk. You also didn't shy away from adding as many ellipses as you needed, despite having to freehand them. And of course, I can see the wealth of work you put into figuring out how to lay out the spokes of your rims - each of which you constructed with consideration not only to the outward face, but also the structures' side planes, so as to make them appear solid and three dimensional.

Now when I saw that you felt you'd improved in your understanding of cast shadows, I was initially... a little concerned that I would have to explain that in fact you hadn't. But going over the set and really looking at each one carefully, I realized that you were in fact quite correct. It's not that common, strangely enough, to see a lot of growth over a limited set of 25 of anything, but it's clear that in your highly analytical, studious manner, you absolutely did. At the beginning you were falling into the trap of filling in side planes with solid black (which is more akin to form shading rather than cast shadows), and you frequently also conveyed the textural forms through pure construction (in other words, explicit markmaking). But over the course of the set, I did see you coming to understand the nature of the forms you were dealing with.

In the end, with wheel 23, you brought it all together to imply the presence of those textural forms without needing to draw them first.

Sure, it would have been great to have that be the case for all of them, but only on the most superficial of levels. In fact, most students simply don't use cast shadows on this challenge, because being as far removed from Lesson 2, they simply forget to address this challenge as a textural one. In that sense, it's something of a trap - a rude awakening to remind students that the textural concepts exist, and that they should review them prior to finishing up the rest of the course.

Now there is one area in which I want to provide some advice, and that's in the cases with very shallow, or very narrow grooves. These are very similar to the issues we run into in textures with prominent holes or cracks - in effect, the student focuses on the hole/crack/groove as though it is the textural form. Of course it's not - it's an absence of form. This causes students to simply fill those areas in - which we can see in 24 and 25. Instead, we have to focus on the walls around the textures, which cast their own shadows into the groove (but not always filling it in).

Here's a diagram which explores how to think about these kinds of textures, and how to tackle them. This won't always change the results of how you depict such a texture, but it does make a big difference in how you think about it, and then how you extend those concepts to other textures where it does have an impact.

So! I'll go ahead and mark this challenge as complete. Congrats on the growth.