Looking over your work here, overall you're moving well in the right direction, although there are a few things that I can suggest to keep you moving on the right track, and to help you yield further improvement with your textures. These suggestions will fall into a few categories:

• Working exclusively with shape

• Handling cases of "negative" space in textures

• Pushing for more even transitions in your gradients

Working exclusively with shape

The main point that is holding you back with your textures is that right now the marks you put down on the page as you build up your textures are both line-based and shape-based. Line-based marks unfortunately have a tendency to lean us more towards the kind of explicit markmaking that we really want to avoid, as it involves drawing either the textural forms directly, or it involves us drawing what we see on the page without giving as much consideration to the textural forms that are present there along that surface.

Instead, it helps a great deal to shift towards working with shape exclusively - that is, first outlining our intended cast shadow shape, and then filling it in, rather than drawing any one-off marks. You can see an example of this in the Lesson 0 tools video, where I demonstrate the use of brush pens here.

The reason this is beneficial is because it gives us a specific step that focuses entirely on the design of the intended shape. Design can be thought of as the same as "thinking". That is, in having to design those shadow shapes, we have to actually consider not just what we see in our reference, but the forms they represent. From there, we have to consider the relationship between the form casting the shadow, and the surface receiving it. It's this spatial relationship which is captured, represented, and conveyed to the viewer entirely through the design of the shadow's shape. In the absence of intentional design, we end up more with arbitrary marks, or marks that are drawn based purely on copying something you see - in which case you're much more likely to make little mistakes that undermine the actual forms that are present on that surface.

To that point, it's not every mistake or inaccuracy that has a negative impact. Some are entirely benign, while others will completely flatten out the result. Understanding what it is you're actually trying to convey, and how the marks we draw relate to it, rather than simply copying what we see is critical to avoiding the mistakes that do the latter.

Handling cases of "negative" space in textures

There are certain textures - like those featuring cracks, holes, or grooves - which tend to lead students astray. They do this more prevalently than other textures because the "named" elements of those textures (the aforementioned cracks, holes, and grooves, the things you can actually ascribe names to) don't refer to the textural forms. Rather, they refer to an absence of form or space - to negative spaces. Students end up approaching them as though they represent the form directly, and so in seeking to draw those forms (because they're still focusing on explicit markmaking, on drawing what they see, etc.) they simply fill in the cracks, the holes, the grooves, etc.

This diagram goes into why this is incorrect, and the fact that it is the walls that surround such negative spaces that are the actual textural forms in question. So, going forward, be sure not to be distracted by the wording, and always seek to identify the textural forms in play. This will be especially relevant to the 25 wheel challenge, as the visual difference can be quite subtle (between filling in shallow grooves vs. actually drawing the shadows being cast by the walls surrounding them), but it's all about the little differences that arise from the manner in which the student is thinking about the task before them.

Pushing for more even transitions in your gradients

This last bit will be short - basically, right now while you are putting effort into having the black bar on the far left blend more seamlessly into the rest of the texture, it's still very much crushed to that end, with the transition being limited to a small stretch of the gradient. Instead, try and have the "darker" portion of your texture take up more of the space towards the left. This will give you much more space to work in smaller bits of light, gradually increasing this and allowing more gaps between your cast shadows as you progress towards the right. This of course will also be much more time consuming - but that's the nature of the exercise. By crushing the blacks further to the left in this manner, you definitely did cut down on a lot of the labour that was necessary for this challenge, so be sure not to do so in the future.

With that, I'll go ahead and mark this challenge as complete.