Your work here is really well done! When it comes to the constructions, you've laid out your ellipses well, all aligned nicely to the central minor axis line, and you didn't just stick to the bare minimum of ellipses required for a cylindrical form. I can see you adding additional rings to help add greater complexity to these solid forms, identifying how the tires have more bevelled ends, with a middle section that swells out a little further.

I can also see clear signs that you're mindful of the textural nature of the tire treads, as you mentioned yourself. You're definitely making a clear effort to avoid the kinds of things the texture section of Lesson 2 tries to steer you away from, and while there are still a few issues I'll point out, you are definitely moving in the right direction as far as that goes.

Lastly, you've done a great job of capturing all the complexity and nuance in every aspect of these wheels - from the construction, the tread, and even the various kinds of rims which often can be quite tricky to pull off (given their division of space in three dimensions).

So, on the topic of the tire tread, you did do a great job but there are a few cases where I think a little more advice can certainly help. Looking at wheel #11, this is a case where you definitely fell back into thinking in terms of outline instead of cast shadows. I'm not going to dwell on it too much, as the odd slip-up is not a big deal, but it's still worth pointing out.

Looking at wheels like #5 and #16, I do see that you were clearly trying to work in terms of shadow, but there are two issues here:

• As with 11 (and also 24), you did end up outlining these forms. In general, really try to avoid working with outline altogether when tackling any texture. Instead, you can try to get in the habit of purposefully drawing shapes rather than lines - that is, where a line starts and stops at different points, a shape encloses an area. You can get in the habit of ensuring every mark you draw actually encloses a space which is then filled, as shown here. Creating a circuit instead - where the start/end points are the same - which is then always filled with black, you're forced to think in terms of more than just a simple stroke. Otherwise it can be very easy to just draw lines around our form instead of thinking in terms of cast shadows.

• You also ran into an issue where you actually ended up drawing your shadow shapes on the form itself, instead of on the surface around the form. This is a common mistake that occurs when we confuse form shading with cast shadows. Form shading is where a surface gets lighter as it turns towards the light source and darker as it turns away, and we generally avoid adding it to the drawings for these lessons. Cast shadows on the other hand don't go on the form in question - instead it falls on the surrounding surfaces. Here's what I mean. Notice how on the left there, it's just filling in certain faces of the box, but on the right side we're able to see the full clear silhouette of a box, and able to perceive those different planes purely from the shape of the silhouette itself? That's what you want to achieve.

So! All in all, your work here is really well done. There's still some stuff to work on, but you're absolutely ready to move on. I'll go ahead and mark this challenge as complete.