To quickly touch on your question, that is incorrect - it's not that the major and minor axes switch directions, it's that the proportion of the plane that your ellipse is being drawn into is very far from matching the criteria of it being square in 3D space. In other words, that plane ends up being very rectangular. That isn't in and of itself a mistake as far as the exercise is concerned - we are not expected to get those proportions correct each time (I'll expand on this further when I get to the cylinders in boxes portion of the critique). What is a mistake however is in such cases altering the instructions as to how the line extensions are to be applied, so definitely keep identifying the actual minor axis of the ellipses.

Anyway, jumping in with the cylinders around arbitrary minor axes, your work here is largely well done. You're varying your rates of foreshortening nicely, and your linework is all looking confident and well planned. I'm pleased to see that you're quite fastidious in identifying the correct minor axis lines for your ellipses here, and that you're not just catching the more obvious mistakes - you're also identifying those that are subtler and frankly quite easy to miss. This is important, because as our skills progress, we have to be more and more attentive to the little discrepancies to avoid having our growth plateau.

Continuing onto your cylinders in boxes, by and large your work here is well done, and the issue you were asking about doesn't come around often enough to be a significant issue in this set of homework, but it is something to keep in mind going forward. 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.

So circling back to the issue you were asking about, generally what I'd recommend is focusing on two main things:

• First aligning your ellipse as closely as you can to the minor axis you know you want to follow (which would run down the length of the cylinder)

• Then ensuring your ellipse touches all four of the side edges of the plane

If the plane itself isn't proportionally square in 3D space, your line extensions simply won't come out all aligning perfectly - but we're not here to execute the work perfectly, we're here to perform the exercise and allow it to help improve our skills, little by little. In order to do this, we have to ensure that the line extensions - the analysis we perform - is telling us the truth. If we swap the minor axis/major axis as you did in some cases, we stop getting useful information from that process.

So, just be sure to keep that in mind going forward. I'll go ahead and mark this challenge as complete.