Over the course of the set, I can definitely see that you're making a concerted effort to focus on the use of cast shadows in this exercise. That's important, as the purpose texture serves as a concept in this course is to bring everything back around to spatial reasoning and spatial relationships, and those cast shadows are what allow us to convey the relationships between the forms casting them, and the surfaces that receive those shadows. So in that, you're doing well - but there are some key points that I want to call out and suggest to ensure that when you apply this exercise in the future, you'll be in a position to leverage it to its fullest.

The first point is that as discussed in these reminders from Lesson 2, it is best to get in the habit of making all your shadow shapes (at the very least within the bounds of what you do from this course) using the two-step methodology of first outlining and designing your desired shadow shape, then filling it in. The reason this is so important is because it forces us to break away from the temptation of simply drawing our textural marks as we observe - a process that can easily cause us to skip the "understanding" phase outlined in those reminders, by instead requiring us to actively think about the shape we want to create not as part of a larger process of painting it in stroke by stroke, but in its entirety, right then and there. This ensures that the shape of the shadow (even if it ends up being merged into other intentional shadow shapes later on) is the primary focus, rather than the aesthetic result the marks build up to. It also reinforces the focus being on the spatial relationships, since the shape we design, as mentioned above, is what establishes the relationship in three dimensions between the form casting it and the surface receiving it.

The second point is an aspect of the exercise you seem to have largely forgotten about in its entirety - that is, the purpose of the solid black bar on the far left of our gradients. As discussed here in the instructions, the purpose that bar serves is to give us a reminder that we are creating a gradient from black on the left, to fully white on the far right (where another solid bar, this time white, sits). The goal of the exercise is to create a seamless transition from one to the other, using the shadows cast where your textural forms block the light coming in from the far right. The closer the textural forms are to that light source, the shorter the shadows are, whereas the farther they are, the farther the shadows themselves will be thrown due to the shallower angle of incidence from the light source (as illustrated here). Approaching the far left, those cast shadows get thrown farther and farther, allowing them to merge together into a large mass which in turn allows us to reach this goal of obfuscating the edge of the black bar - in other words, making it impossible to identify where the bar ends and the texture gradient begins. This aspect seems to have been largely forgotten about, as the majority of your texture gradients jump suddenly from solid black to a complex combination of black and white shapes/marks, making that hard edge of the black bar very obvious.

The last thing I wanted to mention is more generalized, but it's important to keep in mind. Students generally assume that the best way to gauge the success of an exercise is in how it looks at the end - in the case of this exercise, many will be tempted to consider a result that looks identifiably like whatever texture they were using as reference, that it's more successful than one that does not. This is not however the case, and is generally not the case for anything within this course. Instead, it all comes down to the process we apply - not the outcome it yields. It is entirely possible for the steps to be followed as instructed, focusing entirely on shadow shapes, and designing those shapes with care and intent, and to have the result not be something a third party would be able to identify at a glance. That's entirely okay, as long as the steps that were followed were those instructed, because it's not going to be the resulting drawing and how identifiable it is that actually teaches us about how these forms exist in space together. It's the process of considering each individual textural form, determining what kind of shadow it would cast, and then applying that shadow to the surfaces around the form - a process that has us thinking about different kinds of spatial relationships - that provides the value in the exercise. So keep that in mind, even beyond what we explore in this course, as it's a good example of how chasing a visibly impressive, detailed, and identifiable end result isn't always a sign that things are going in the best possible direction.

Anyway, I'll go ahead and mark this challenge as complete. Be sure to keep these points I've raised in mind when practicing this exercise in the future, or when tackling anything to do with texture when the focus is on spatial reasoning.