Starting with the cylinders around arbitrary minor axes, while you do ultimately come around and sort the major issues out, this exercise does appear to have a fairly rough start. There are two main issues that stand out to me here:

• You frequently draw cylinders which appear to intend for the side edges to be parallel on the page (in other words, forcing the vanishing point to infinity). This is an issue that is addressed here in the instructions. Those notes explain why this is incorrect.

• This issue seemed to diminish around the 60-70 mark, but around that same time I saw an increase in cases where the minor axis lines you were marking in afterwards were showing some notable signs of confusion. As you can see here, there are a lot of places where you've confused the minor axis with the major axis, which would definitely have an impact on how useful that error analysis ended up being. Can't correct mistakes if we miss them in the first place.

• In the image from the previous point, I marked one towards the bottom with a star. This is a case where you appear to have reversed your degree shift - the farther ellipse should both be smaller in overall scale, and wider in proportion. You appear to have it smaller in overall scale, but proportionally narrower. This isn't an issue that came up too often, but I did see it here and there throughout the remainder of the set.

Ultimately while you still do continue to make mistakes (for example, like the last point above the bottom right of this page shows an example where the closer end is smaller in its overall scale, which contradicts the core principles of perspective), by the end of the set they do not appear to follow the same kind of patterns they did earlier, which suggests to me that while you absolutely need to give yourself more time both in going through the instructions more carefully and in ensuring that you've got ample time to apply those instructions and steps mindfully and consciously, ultimately the understanding is there. You just have a tendency to be a little careless here and there. Ultimately that is not something that can be corrected with an explanation of theory, but rather will have to fall to you.

Continuing onto the cylinders in boxes, your work here is generally a fair bit better, without much in the way of notable issues. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

There's just one small thing that could be hindering you in getting the most out of this error analysis approach - when applying line extensions to your ellipses' minor axes, you appear to be applying more of what we did in the previous exercise, in terms of simply identifying those minor axes. What you should be doing here is ensuring that they are extended as far back as the other lines, so you can more easily compare them and judge their convergences.

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