I can assure you that ending up with a smaller ellipse guide (and thus smaller wheels) is pretty normal. Full ellipse guides are prohibitively expensive, and while we're looking into one day being able to produce and sell our own for far less, for the time being most students use a master ellipse template, which includes a variety of degrees but with a cap on how big they get. So, nothing to worry about there.

Jumping right into the first focus of this challenge, let's look at your wheel constructions. On this, you're doing a great job. Not only are you mindful of building out your various wheels with several ellipses to capture the more complex, "inflated" profile for the wheel/tire, you're also taking care with your rims to draw not only the front face, but also the side planes of those structures to make them feel more solid and three dimensional.

The second part of this challenge comes down to the tire treads - or more specifically, it's a trap. Given how far removed we are from Lesson 2, where we discuss texture and the concept of implicit markmaking, it's not that uncommon for students to have forgotten about how it all works, and a surprising number of them just try and make do with what they remember, instead of revisiting that material.

You, on the other hand, did not fall into this category - as I can see it, while there is definitely room for improvement and some things I can call out to help you along that path, it's clear to me that you have been mindful of trying to work implicitly. That is a big step ahead of those who attempt to just apply construction (outlining, drawing all the internal lines, and so on), which results in a higher density of linework and creates unintentional focal points. While that may not be a big deal for wheels that are floating around in the void on their own, it does become a problem when drawing, say, a car. The dense tire texture would draw the viewer's attention whether you want it to or not.

But fortunately that's not an issue! I did notice two things I want to call out however:

• There are quite a few tire tread textures where you rely more on somewhat arbitrary marks, especially when you get more into the sparser areas of the texture where you can't more or less outline the entirety of the textural form. This usually happens when the student isn't taking the time needed to really understand how each individual textural form sits in space. Rather than identifying a specific form, understanding how it sits in space, and how it relates to the surfaces around it, then finally designing a cast shadow shape that defines that specific relationship (all of which takes a LOT of time and patience), it's rather tempting to just try and "wing it" and put marks down, hoping that they'll be close enough to create the specific impression we're after. Unfortunately, texture is time consuming by its nature, and to avoid that aspect of it merely gets in the way.

• I also noticed that when working with those filled areas of solid black, rather than actually designing an entirely separate cast shadow shape, you tend to instead just fill in spaces that already exist - usually the side planes of the textural forms themselves. This is a common misunderstanding, and is more similar to form shading rather than cast shadows, and I've marked out a little explanation here on another student's work. Along the top, we've got the structural outlines for the given form - of course, since we want to work implicitly, we cannot use outlines. In the second row, we've got two options for conveying that textural form through the use of filled black shapes. On the left, they fill in the side planes, placing those shapes on the surface of the form itself, and actually filling in areas that are already enclosed and defined on the form and leaving its "top" face empty. This would be incorrect, more similar to form shading and not a cast shadow. On the right, we have an actual cast shadow - they look similar, but the key point to pay attention to is shown in the third row - it is the actual silhouette of the form itself which is implied. We've removed all of the internal edges of the form, and so while it looks kind of like the top face, but if you look more closely, it has certain subtle elements that are much more nuanced - instead of just using purely horizontal and vertical edges, we have some diagonals that come from the edges of the textural form that exist in the "depth" dimension of space (so if your horizontals were X and your verticals were Y, those diagonals come from that which exists in the Z dimension).

So! Be sure to keep those points in mind, but I'll go ahead and mark this challenge complete all the same.