Starting with the structural aspect of the wheels, you're doing great. Despite working with the limitations of the smaller master ellipse template, you've still demonstrated a great deal of effort in executing the marks capturing fairly small structures with a lot of care and patience, and so you didn't really lose much to the small scale of the drawings. Your wheels' overall structure features a nice arcing profile, which helps to convey a sense of inflation to the tire, so that it'd land with a bounce rather than a heavy thunk, and I can see that you've generally attempted to define not only the outward face of your rims/spokes, but also the side planes, helping to avoid them from flattening out.

Onto the second aspect of the challenge, here we get into something of a trap - and one that you've certainly fallen into, as many students have. This section focuses on texture, and the trap is that a great deal of students tend to overlook the clearly textural nature of the tire treads, and end up approaching it more in a decorative fashion rather than referring back to the material from Lesson 2 to refresh their memories on how they should be tackling it within the context of this course. As a result, there ends up being a lot more drawing from direct observation, rather than consideration of how, as explained here, the textures are made up of individual little forms arranged on the surface, which are then implied by drawing the shadows they cast, rather than being drawn directly (whether constructionally or with one-off lines and marks).

Thinking of each shadow as a specific filled shape that they conveys the relationship between the form casting it and the surface receiving it is very important. It's not something we can do just by observing our reference, but rather requires us to understand how it sits in 3D space - going beyond the simple 2D information we might glean from the reference if we weren't thinking about what it is meant to represent.

In addition to this, when dealing with textures that are composed of holes, or even grooves (as many of your tire treads do), it's easy to think that the textural forms are these grooves - but they're not. The textural forms are the walls that rise up around this negative, empty space, which cast shadows upon one another and onto the floor of the groove itself. This diagram goes into this further, and should help drive the concept home.

In addition to this, here are some additional diagrams that may help you in understanding the reminders from Lesson 2 I linked you to above:

• https://i.imgur.com/2Oo6qIb.png and https://i.imgur.com/spgJI6n.png are different versions of the same diagram (in case one makes more sense to you than the other), which helps to depict the manner in which we can think about textural forms. This relates more directly to the texture analysis exercise, but can of course be applied in general.

• And https://i.imgur.com/tJIFFQA.png is a more direct application of those reminders and the previous diagram(s) in the texture analysis exercise - but again, this is useful in applying texture in general.

Now, as this part of the challenge is an intentional trap, the goal is not to hold you back on its account, but rather to give students something of a rude reminder that they're neglecting concepts that they have gone over. So, be sure to go back and review the material from Lesson 2, in conjunction with the additional diagrams I've provided here. I will still be marking this challenge as complete.