Given the limitations of the master ellipse template, I think you made the right call in setting aside the degree shift within a single wheel, and focusing on scale. It also isn't really that incorrect, since the relative distances between one end of a wheel to the other, unless it's really wide, or we're looking at it from very close up, the foreshortening will be quite shallow to begin with.

When it comes to that core construction of the wheels, you've by and large done a really good job. You've paid a lot of attention to the structural elements in place, minding the fact that things like the spokes of the rims don't just exist as flat shapes sitting on the face of the wheel, but that they also have thickness to them that is necessary to capture and convey. You've shown a lot of clear attention being paid to the 3D nature of these structures, resulting in wheels that feel solid and believable.

The area where this challenge really serves its purpose however, is in how we tackle the tire treads themselves. Being that they are made up of forms arranged along the simpler cylindrical structure of the wheel, they very much fit the definition of texture as discussed in Lesson 2. Being as far removed as we are from that lesson however, it is very common for students to forget about the principles explained there, the concept of explicit vs. implicit markmaking, and how we want to focus on drawing the shadows our forms cast, rather than drawing those textural forms directly. It's for this reason that this challenge is intended to be a bit of a trap, to help remind students that they may want to review the concepts from earlier on in the course before they continue forwards to complete the last lesson.

One of the reasons this use of implicit markmaking (where we draw the cast shadows and not the forms that cast them) is so critical is that it allows us to control the visual density of a given object, while still conveying the texture of its surface. While the wheels as you've drawn them here are entirely fine when just floating in space, when we actually use them as part of a larger vehicle construction, they're going to create focal points, with their densely packed arrangement of light and dark grabbing the viewer's attention whether you want it to or not.

Conversely, using cast shadows allows us to change the nature of the marks we use to imply the presence of those textural forms (by making our shadows either deeper and heavier, or smaller and lighter), without actually changing the nature of the texture being conveyed. It relies heavily on using the viewer's own brain to fill in the areas left blank, whilst providing them with the clues they need to do that in what minimal texture is added. This is the basis for the kind of "implied detail" you'll see in many illustrations, and you can see an example of this, where the nature of the marks changes while the texture itself remains the same, in this demonstration of african bush viper scales.

Now, in terms of specifically where your approach is going wrong, falls into two main categories:

• You're drawing your textural forms directly, applying the same constructional techniques we'd use for other standalone structures (like outlining forms and whatnot). Students are often hesitant to dive into just laying out the cast shadows, because it's quite daunting to try and keep track of the forms that are present on that surface without drawing them. Of course, the only way in which we can really improve on that front is to try even though it's daunting, but many students end up forgetting about it altogether. One thing I find to be quite helpful are the reminders on what to keep in mind when tackling texture listed here.

• The other issue - and this one actually came up way less frequently, since most of the time you were focusing on just outlining your textural forms - is that when you did use filled areas of solid black, you tended to use them to fill in the side planes of your textural forms as we see here. Remember - we want to use cast shadows, which means introducing new shapes that themselves define the relationship between the form casting the shadow, and the surface receiving it. If you find yourself filling in a shape that is already present, then take a step back and ask yourself whether what you're doing is more akin to form shading instead.

The last quick point I wanted to call out is some advice on how to think about textures that are made up of holes, or grooves, or cracks. Situations like this, where the actual thing you can name to describe the texture (holes/grooves/cracks/etc) are in fact not something that constitutes an actual form, but rather a negative space, or the absence of form. Students tend to focus on just drawing the thing they can name, but in this case it makes us extra prone to think purely about what we're observing, and not what it actually represents in 3D space. These notes go into this issue in greater depth.

Now, rest assured - this challenge is designed as a trap, which means you're kind of expected (to a point) to fall into it. So, I'm not going to be assigning revisions, but rather I'll simply ask that you use the information I've provided here to go back over Lesson 2's textural concepts on your own, before continuing ahead. So, I'll go ahead and mark this challenge as complete.