Tired though you may be, you've done a great job here! You've invested a good bit of time and patience into what the challenge asked of you, and I'm quite pleased to see that you were working with an ellipse guide, so as to keep as focused as possible on the specific concepts explored here.

This challenge breaks down into two main components. First off, there's the core construction of each wheel. You tackled a wide variety of wheel types here, and with them you explored a lot of different kinds of rims and spokes. Given that the ellipse guide limited how large you could work, some of these would definitely have been quite challenging, but all the same you did quite well. While I noticed that maybe a couple (like 19) had spokes that got a little flat (in that particular case, we don't really have any implication of the thickness of those rims, but at that scale I can certainly understand why). Most of the others did include consideration for the thickness of those forms however - like 15 and 16 for instance. Another point that stands out in terms of your strengths here is how you spaced out those with a variety of spokes - very nicely done.

Along with that, I'm pleased with the overall structure of the wheels themselves. You made a good use of additional ellipses, even with the master ellipse template's limitations, to go beyond the basic rigid cylindrical structure and including more "steps" throughout its length.

The second component of the challenge is, as you noted yourself, exploring texture for the first significant point since Lesson 2. Many students have a tendency to forget the principles of implicit markmaking, so this challenge serves as a bit of a trap, catching anyone who may have let it slip, and refreshing their memory before the end of the course. In your case however, you've honestly handled this really well. You remembered to stick to working with cast shadows, implying the presence of the various tread forms along the surface of the tire.

For this aspect, I tend to look most closely at the tires with "chunkier" treads. Those with shallower grooves tend to get by more easily whether one uses implicit or explicit mark making, but those with larger textural forms tends to force students to show their cards. Wheel 3 for example is an excellent example where you clearly focused on the nature of a given textural form, and then drew the specific shadow it would cast on its surroundings. You didn't fall back onto outlines, and you also ensured that the shadow shape you drew fell on the surfaces around the textural form, rather than filling in one of the form's side planes instead (which is also a common mistake students make). In number 13, I can see you working through similar problems, while also figuring out how those cast shadows would behave as they move away from the light source, inevitably becoming deeper and broader. These are tricky spatial problems that you're dealing with here, and you're handling them quite well.

I really have just one criticism to offer in this regard - way towards the end at number 24, I feel like you dropped the ball a little, in terms of how much time you invested into each of those shadow shapes. That's not such a concern to me though - it's normal to have off-days, or wheels that just don't come out well (and that particular tread pattern, with its curving lines can be quite challenging despite its apparent simplicity). What I wanted to call out is how you tackled the top and bottom, filling it in with solid black, as if to apply form shading to the wheel structure, separate from the tire texture itself. Don't forget - as discussed here in Lesson 2, we leave form shading out of our drawings in this course. Conversely, while number 18 is similar, you ease gradually into those larger black shadow shapes, showing that they are in fact an amalgam of all the smaller cast shadows (rather than just an arbitrary bit of shading).

Anyway! All in all, your work here is very well done. Keep up the good work, and consider this challenge complete.