To answer your question, I recommend the use of ballpoints because regular ones (so not gel pens which have really rich, dark ink, but the more common ones that behave more like mechanical pencils aside from their permanence, allowing us to make light strokes that barely make a mark on the page) make our marks somewhat less of a complete commitment, and allow us to address little issues before we entirely commit to a given direction. Conversely, fineliners will make strong commitments with each stroke, not really giving us much room to pivot.

Anyway, jumping into the challenge by first focusing on the structural aspects of your wheels, you're generally doing quite well. You're employing a lot of different ellipses throughout your structures - going well beyond just building a basic cylinder, but imbuing the structure with an arcing profile that does a great job of capturing how the tires are inflated, rather than solid all the way through. I'm also pleased to see that in general you are mindful of not just defining the outward faces of your spokes/rims, but also defining their side planes to establish them as fully three dimensional structures and not just focusing on the outward face (which would appear more flat).

The second aspect of this challenge is about texture. In this regard, the challenge is something of a trap, in that most students don't go back and review the textural concepts from Lesson 2 (and often forget that those notes even exist, choosing instead to just tackle them however, with more of a focus on decorating their drawings over actually considering how texture focuses on the relationships between 3D forms just as construction does.

Now, I can clearly see that you did not entirely fall into that trap - you were aware of the relevance of Lesson 2's concepts here, although there are some ways in which your use of those concepts can be improved. The most significant of these is the specific way in which you're actually drawing your filled cast shadow shapes. Right now you're drawing them quite haphazardly, effectively "painting" them on one stroke at a time. This results in indistinct shadow shapes with no clearly defined design to them.

Instead, it helps a great deal to approach these in a two-step process - first drawing the outline of your desired shadow shape, then filling it in. Being able to draw that outline separately allows us to actually think about how we wish to design this intended shape, and thus consider how its specific design establishes the manner in which the textural form relates to the surface upon which the shadow is cast. This two-step approach is demonstrated in this video from Lesson 0 (in the section where we talk about the use of brush pens, there should be timestamps in the video description to each section), although the same principle can certainly be used with ballpoints (though you can also choose to use a fineliner or brush pen to fill those shapes in as well).

At the end of the day, it is important to keep in mind that working in a smaller space is inevitably going to require more time to think through each individual stroke you wish to make. If we're prone to working with an idea in mind for how long things should take, then we're more likely to rush through parts, not giving marks that require more time, in order to meet that expectation. It's the complexity of the task that decides how long things should take, not how long we feel they should.

Now there's two last things I want to call out:

• The first of these is that due to the somewhat rougher, unclear nature of the particular shadow shapes you're working with, it's unclear as to whether or not those shapes capture the shadow that the textural form would cast on its surroundings, or if you're thining more in terms of filling in the side planes of the textural forms themselves (which would itself be more akin to form shading, which as discussed here is not something we incorporate into our drawings for this course), or if you're designing entirely separate shapes that define that kind of relationship between the textural form casting the shadow and the surface receiving it. Just in case you are indeed thinking in terms of filling side planes instead of inventing new shapes for your shadows separate from those that already existin the drawing, I would recommend that you give these reminders a read.

• It's very easy to look at textures that are composed of holes or grooves, as though the holes/grooves are the textural forms themselves. They're not - they're an absence of form, and the form would be the walls surrounding the empty space, which cast shadows onto one another and onto the floor of the hole/groove, but this can result in students focusing more on drawing the grooves themselves, and not thinking about the difference in what they're attempting to convey. These notes go over thus further, so be sure to keep this in mind going forwards.

I am going to be marking this challenge as complete, but do be sure to review this material thoroughly - what I've referenced, what I've linked, and what I've stated here.