Over the course of this challenge, I can definitely see a fair bit of core understanding as to the concept of texture and how we engage with it throughout this course - really digging down into the fact that it's made up of small forms, and that every mark we put down on the page is really just a shadow being cast by those forms. Earlier on you certainly were less comfortable with this concept, and tended to try and introduce other sources of black - for example with number one, you laid down your basic vein structures, but then to blend back into the solid black bar on the left of the gradient, you introduced a completely separate black area, as though a shadow were being cast onto this surface by some other entirely different object held above. Similarly in the second one, we see various attempts at using more hatching-like techniques. Overall though, you've definitely pushed yourself quite continually towards thinking more and more about the forms that are present, and the shadows they cast.

The issue we see in texture 1 does persist for a bit (that is, the separate cast shadow being applied on top of everything with no visible source), but over time you drift away from that approach. Just for the sake of completeness though, I do want to state that this is a pretty normal mistake to make, and the idea that the heavy black we get in the far left comes from the existing shadows being cast by the textural forms comes from those shadows simply getting that much longer and deeper can be very difficult to wrap our head around.

To illustrate this concept, I've got this diagram (and this alternative form of it in case it makes more sense to some people) to help explain exactly what's happening. Basically, on the far right side where our texture is whittled down to just plain white, we can say that we're very close to the light source, and it's that proximity that is causing the forms' shadows to be cast only very minimally due to the steep angle at which they receive the light's rays.

As we move further out to the left, the angle of those rays gets shallower and shallower, and so the shadows they cast become longer and longer. The more of these shadows are cast, the more they blend together into a singular complex shadow shape, with smaller and fewer instances of actual light shining through where the shadows don't quite cover.

To that point, how much the form protrudes from the surface also impacts the shadow that is cast, which is a point of interest I noticed in regards to texture 16, the bricks from this page. Now, I don't know what reference you were using for this, but it did stand out as being a bit abnormal to me because the bricks appear to protrude a great deal from the mortar arranged between them. We can see this because of the nature of the shadows themselves. Now, if that was simply what the reference portrayed, then by all means, you handled that largely correctly. And even if it wasn't what the reference really looked like, I still wouldn't count it as a mistake as long as it was the result of a conscious decision to pull those bricks further out.

I will point out however that in your textural gradient for that one, the bricks at the far left, as you get close to the black bar, only very suddenly start projecting their shadows way farther than the others. It's more correct than the issues I've remarked upon previously, but the suddenness of it suggests inconsistency in how light is behaving. Really those shadows should gradually be elongating at a consistent rate.

Another point I wanted to quickly call to your attention was something I shared with you when critiquing your 25 wheel challenge. Consider what's explained in this diagram in relation to the cracked texture you included in the middle of this page. Overall you've done a really good job in dealing with the complexity of the cracks themselves, and observing them correctly (especially in the direct study on the left), but it does still appear that you're filling in the cracks completely, rather than considering the shadows being cast from the walls around the cracks, upon each other and upon the "floor" at the bottom of the cracks.

Overall, there's definitely a lot of improvement throughout the set, although there are still some little hiccups that come up even towards the end. For example, for the texture in the middle of this page, with the interlocking paving stones, you appear to lay down the outlines of the structures themselves, rather than focusing only on drawing the shadows they're meant to cast. This leaves you with the notable issue on the far right (where the texture is supposed to shift towards being completely white), where you now have to pick lines at random not to include. That's a tell-tale sign that this wasn't considered in terms of being textural forms casting shadows, but rather trying to draw a pattern as a whole.

Conversely, the ice cream cone texture preceding it is an excellent example of how we focus on the forms and the shadows they cast. So by and large, you're making a lot of progress, but are still prone to forgetting the core principles of the exercise at times.

The last thing I want to mention is that choosing a complex texture (like the one you did at the end, which demanded an enormous amount of time from you) isn't... actually better than picking any of the other textures you'd encountered. More complex doesn't mean more valuable as an exercise - it just means it's going to take a lot more time. You've certainly demonstrated a great deal of patience and discipline in tackling it, but going forward I would not recommend doing this in the future.

Anyway, getting back to more positive things, I'll go ahead and mark this challenge as complete. You've done a great job, and have certainly shown a great deal of growth.