Hey there wombat, great job finishing the challenge! You've put in a lot of good work and should be proud of your accomplishments. Throughout the challenge you have made great strides in your line quality, your sense of form and space, and overall sense of how lines should be converging. You have also done a good job playing around with different types of boxes in terms of scale, orientation, and rate of convergence.

So while you have done a good job getting your convergences under control, there are still some times when you have skewed lines. This is totally normal at this stage and uncomfortable has made this infographic to dive further into the topic of parallel lines in perspective. The key point of this infographic is how we need to view these lines - they are an ensemble all related to one another by the vanishing point. As the vp moves, the angles between the lines change. This means all lines are all connected to one another and as anything changes, everything changes. Often times students will draw a box plane by plane which is a pretty common approach. The way beginners do it is to focus on one plane, making sure all the lines are going off in the right trajectory and then moving on to the next plane. When they draw the next plane they don't take into account the lines they previously put down. This results in multiple points of convergence instead of the one true vanishing point, as indicated in boxes like #227. It takes a while to be able to step back and consider all the lines simultaneously, but as you practice this it becomes more intuitive and things start to fall into place.

One more thing I would like to mention is line weight. Line weight serves the purpose to reinforce the solidity of our forms when done well, and breaks the solidity when done no-so-well. Many of your boxes have the heaviest part of the line in the center where you start your stroke and the lightest around the perimeter. This means you would need to reinforce your weight around the perimeter to bring solidity back to your boxes. Remember: when applying line weight we don't trace lines but rather re-draw them.

You have done a good job here and made a lot of progress. You are now officially finished with your challenge. Congratulations! This doesn't mean you should let yourself get rusty on boxes with the next few lessons being organic heavy. Make sure to keep practicing them in your warm ups and you'll keep the rust away and continue to improve.