First I would just like to say congrats on completing the challenge, it takes alot effort and discipline to complete all 250 boxes.

I can see a ton of improvement of your linequality through your progress of this challenge, towards the beginning your lines were actually quite wobbly but at the end they gained alot of confidence im your lines. this is one of the main purposes of this exercise so well done!

When applying the line extension method make sure are always extending the lines away from the viewer. I can see that some of your boxes still do this incorrectly

(e.g. 249, 247, 229)

Here is a helpful guide taken from Elodin critique guide which shows how to do this correctly you want to use your initial Y to help your figure out the direction they can be extended.

keeping this in mind will also help you cross-hatch the "right" face of the box since it seems like sometimes you are doing this on sides that are not facing the viewer.

in terms of the convergence of your boxes you have improves a lot since your initial boxes but I feel you should keep them in mind a lot more. your boxes dont diverge much but alot of them have paralel lines and in 3-point perspective you should be trying to aim for them to all be converging. try expermient with some dramatic foreshortening which will give you some more practice of this.

You already have a wide variety of sizes and oreintaions of your boxes, so good job on that.

another issue that you have that is widely common with this exercise (even I had and sometimes still do) is the inner corner. This is normal because it is affected the accumulation of all the small mistakes from previous lines. one way to improve this is think of the relationship of all your lines instead of just a pair of lines when plotting them out.

One way that helps a lot of people is to change the order in which you draw the lines, after drawing 2 faces, you draw the inner coner next instead of the final face.

This is also a helpful guide which shows you how to do that (again taken from Elodin Critique guide) which you can also find in the pinned messages in the #basic-challenges channel on the discord sever.

And this explains why doing the lines in this order works.

As you practice this during warmups you will improve on them over time.

One last thing I would like to mention is try adding some lineweight to the outer edges of your boxes. A single superimposed line is enough and it gives your boxes solidity. just remember when doing this that you need to ghost these lines too and only do it once. Confidence over accurace. the guide on the site goes into much more detail

As I said at the beginning of this critique, the main purpose of this exercise is to gain confidence in your lines and you have done that so I will mark this as complete.

The second purpose is to start getting an idea of objects in 3D space but Lesson 2 will help you much more in that.

Dont forget to keep practicing your boxes during warm ups and keep the things I have said in mind. Once you get a lot more confortable in your convergences you can start to take a look at some of the more advanced box exercises.