Very nice work! This challenge splits up into two distinct parts. First, there's the construction of the wheels and their individual components (the overall structure, the rims/spokes, etc.) and the second part is how you handle the tire tread texture, and whether or not you remembered the concepts discussed back in Lesson 2. It's a bit of a trap, this second part - students more often than not have allowed themselves to completely forget those principles they struggled with so much back with the texture analysis and dissections, and so having it spring up here is a good last reminder before we hit the end of the course.

Starting with your construction, I'm very pleased to see that you were working with an ellipse guide - this allowed you to focus on the core of the challenge rather than worrying about freehanding ellipses. At this stage, while students have indeed gotten plenty of mileage with ellipses under their belt, it's generally been in areas where a little less precision was no big deal. When it comes to these more geometric and man-made constructions, having to worry about ellipses becomes a distraction, and I genuinely do not expect students to be able to nail their ellipses consistently enough for this kind of thing just yet. It'll come, but Drawabox is after all the starting point, where you learn how and what to practice and develop to build that core foundation.

The construction of your wheels is well done - you've got that gentle swelling through the midsection that makes them feel inflated, rather than just a stiff cylinder, and you've done an excellent job of planning out the arrangement of your spokes. It's not perfect (I can see that in 17 there was some small spacing issues, for example), but it's still very well done. And more importantly, when you ended up making mistakes, you didn't panic - you rolled with them, ultimately ending up with relatively minor mistakes that could easily be missed or overlooked, rather than big struggles to correct and resolve issues, only making them worse in the process.

Moving onto your tire textures, while there are a few areas where you slipped back into working more explicitly when defining those textural forms, throughout the majority of these you've done really well, and I can confidently say you did not forget those textural principles as most people do.

Tire textures like that on number 10 are very close to what I'm looking for. You're definitely working to imply the presence of those textural forms. The only issue there is that from what I can see, it does look more like you were trying to fill in the side plane of those protruding tread chunks. As shown here, it's better overall to leave the internal silhouette of a given textural form empty, and instead focus on the actual shadow being cast on its surroundings. An empty silhouette, with clearly defined corners, can still imply a three dimensional form, and focusing on the cast shadow itself allows us to define a clear relationship between the form and its surroundings - whereas filling in one plane leaves us with a form floating in a void.

Now there are other cases where you ended up working more explicitly - for example, with number 14, 22, and so on you outlined those textural forms completely. Always resist that urge to outline your textural forms. One approach to avoid this temptation is to force ourselves to simply not use individual lines at all, when handling texture. Making a point of approaching every textural mark with a 2 step process of first outlining a whole shape, then filling it in, can help us fight back the urge to take shortcuts and draw with individual strokes in the first place. It can also yield more dynamic cast shadow shapes, as shown here.

Anyway, as a whole you're doing very, very well. I'll go ahead and mark this lesson as complete, so keep up the good work.