Hey there jinsua, congrats on finishing the 250 box challenge. You have made a lot of progress here in terms of not only your ability to draw a box, but also your overall sense of space and form. Your boxes are more solid at the end, and you have a better sense of how your parallel lines converge. Additionally, your line quality has improved quite a bit, but there is still room for improvement with your line weight, as your super imposed line passes to apply more weight sometimes miss your line or end up wobbly which undermines the overall solidity of the form. Overall though by the end of this challenge you are pretty dialed in with your convergences as indicated by you extended check lines. Because you are doing such a good job with your converging lines I won't get too deep into it, but this infographic explains more of how to approach parallel lines in perspective. The overall gist of it is that we must never view any line in a vacuum, as all parallel lines are affected by one another and all tied together by the vanishing point and as that vanishing point moves, the angles between them change as well. This is why students often start out with multiple points of convergence - because they focus on a single plane then move on to the next one without considering those previous lines that were put down. But like I said, you aren't having much problem in this area so that's great! You have honestly done everything asked of you here - you drew your boxes carefully, you applied your check lines, and you took what you learned from each page and used it to improve from page to page. You also did a good job exploring 3d space by drawing boxes of different sizes, orientations, and rates of convergences.

Overall you have done good work here and I will be marking your challenge as complete. As you continue through drawabox do not neglect to practice boxes in your warm ups as the next few lessons are very organic and you don't want to be rusy by the time you get to lesson 6 and 7.