I’ll be handling the critique for your 250 Cylinder Challenge

-Starting by the cylinders around an arbitrary minor axis, your ellipses are drawn with a good deal of confidence as well as your lines, which means that you are making good use of the ghosting method. However I did notice that some of the sides of the cylinders tend to miss and do not actually touch both faces of the cylinder, this is not an issue, as we are prioritizing confidence over accuracy, and I do have one more important thing to call out.

When it comes to the hatching lines, they are drawn with good confidence but I think that you do have a tendency to rush them especially on the boxed cylinders, remember to go through each step of the ghosting method as explained here, and also keep in mind that each line is no less important for being part of a larger group, so give each individual mark as much time and attention as required to draw them to the best of your ability.

-I also like to see that you have spent a good amount of time checking for the actual minor axis of your ellipses, and you have experimented a good deal with the rates of foreshortening and the sizes of your boxes.

The purpose of this exercise is to understand the relationship between the change in scale from one ellipse to the other (where the ellipse furthest away becomes smaller in size) and the corresponding change in the degree that makes the ellipse furthest away to have more visible width.

Both of these things are manifestations of the same thing, and they cannot work independently of each other, fortunately you do seem to have picked up on this relationship whether consciously or unconsciously.

-Moving on to the cylinders in boxes they are turning out well. 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.

In doing the extensions correctly for most of your boxes (I noticed a handful where you specifically put one of your vanishing points at infinity, and then did not extend those lines - generally I wouldn't put any vanishing points at infinity for this challenge, simply because we're rotating these forms entirely randomly, and the chances that they'd align in such a way that the vanishing point would go to infinity is gonna be pretty slim, but regardless you should still be extending them), you have indeed made good headway in improving your instincts as far as these proportions go, regardless of the orientations of the forms.

-I only have one suggestion when it comes to the cylinders in boxes, your first priority is to align the ellipses to the minor axis, you may be thinking that it is more important to have them touching the four sides of the plane, this comes back all the way to the ellipses in planes exercise, this may result in the contact point lines being off, but this isn’t much of an issue as this exercise is not about accuracy, rather it has more to do with intuition.

Aside from that I do not have more to add. So congratulations upon completing this challenge, I’ll go ahead and mark this as complete

Holy cow these are sick!! I have nothing to say but awesome job!! Keep the pace and you’ll continue to reach new heights!! :D