Starting with your form intersections, just a few minor things which I've marked out here:

• Build your cylinders and cones around a central minor axis lone

• Some of your cylinders' intersections with flat surfaces came out a little stiff/uneven - drawing a full ellipse, aligned to the flat plane, can help pin down the particular curvature

• When dealing with two rounded surfaces intersecting, try to figure out the specific direction of curvature for each and then figure out how to transition from one such curvature being dominant, to the other. The result would be a more intentional S curve.

Your cylinders in boxes all appear to be coming along nicely, though I'd work in a little more foreshortening.

Moving onto your vehicle constructions, at the core of it all you're doing a great job. There's some wacky business in regards to your big shadow shapes (I'll touch on this later) but when it comes to establishing forms that are sturdy, cohesive, and well structured, there's no denying that you're doing extremely well. To be completely honest, I don't really have any concerns about your construction. Even when you get into the smaller elements, you don't deviate from a strong awareness of how everything exists in 3D space, and how the different elements relate to one another.

To be completely fair, you do have some weak ellipses in drawings like this one, but it's completely understandable that ellipses would still be an area where we all need more development, and I don't expect students at this stage to be able to knock out ellipses perfectly every time. It's one of the main reasons I allow the use of ellipse guides - but of course, full sets of those can be pricey.

Anyway, let's talk about shadows! Or more accurately, areas that have been filled in with solid black. In this tank, you opted to fill in the underside of the treads with solid black. As a rule, we want to make sure all of our filled areas are reserved specifically for cast shadows only. That means the shadows that are cast from one form onto another surface, defining the clear relationship between them in 3D space. Either filling an object's surface in completely (local colour), or filling in the side that would be pointing away from the light source (form shading), should be avoided, instead choosing to treat the object like it's covered in the same flat white.

Based on your notes in this drawing you are keenly aware that something is going wrong in your use of those filled areas of black, though not necessarily what. The key issue here appears to be that you're mixing up cast shadows (good!), form shading (bad!) and possibly capturing an element of the reflectivity of the surface of your objects. After all, when it comes to texture, the complete absence of texture is itself something that we can communicate, but primarily through implying its reflectivity. This is something we only really do when we get into proper chrome-like surfaces, where arbitrary bars running along the length of a given form can give it the impression of being very shiny and reflective. This probably wasn't really what you were after with this car.

Instead, the focus should be entirely on things cast by actual forms. Most of the blocked in black shapes in this drawing weren't cast shadows - really only those along the front grill (which came out quite nicely), those cast from the wheel well onto the tires, but not the underside of the tires, and the cast shadow on the ground would qualify as cast shadows. Also, those cast shadows don't appear to always abide by the same light source - but you alluded to that yourself as well.

In the submarine, you definitely pulled things back, which is definitely a good thing. While your cast shadows still could use more planning and consideration of the relationships between the forms (which for all intents and purposes, every other aspect of your drawing suggests you understand quite well), this is a move in the right direction for the most part.

As per your notes under that drawing, you mentioned trying to figure out how to draw cubes in 2 point perspective - I'm honestly a little puzzled, because you show in other drawings use of the technique employed in this video, which effectively does just that.

Continuing on, I honestly do think that you're getting a stronger grasp of how to leverage your cast shadows - like in the space shuttle, where there's a much lighter, subtler touch. The big black plane on the side technically falls outside of the rules of Drawabox, but compositionally speaking it's a nice touch.

The last thing I wanted to say is that I'm very glad to see that you picked up on the fact that you didn't have to finish a drawing in one sitting. You complained at one point about hitting the 3 hour mark and getting exhausted. It's completely understandable that working that long in a single stretch (or even over the course of a single day) is a lot - but there's no one saying that once the clock strikes midnight, you must consider the drawing complete.

Some students completing this lesson - veedraws for instance - had a pretty hefty time sheet, but the additional patience and spread objectively yields better results. I'm honestly pretty surprised that you were achieving what you did in such a short period of time. This motorcycle for example looks great and has a great deal of careful subdivision, measuring, and complex detail, and only took ~150 minutes total? Damn.

Anyway, I am as a whole very pleased with your results here, and you should be proud of what you've achieved. I'm happy to mark this lesson, and with it the entirety of the course, as complete. Congratulations!