Jumping right in with your form intersections, to start you're making good progress here, drawing forms that feel consistent to one another within their shared space. Your intersections themselves are generally coming along well - those between straight/flat surfaced objects are demonstrating a solid grasp of how they relate to one another in space, while those with curving surfaces are still a little more hit-and-miss (though that's still pretty normal at this stage.

I've drawn directly onto your first page to point out a few little issues to keep in mind. One thing that helps a lot, especially when you've got two different curving surfaces intersecting with one another (like the cone/sphere intersections towards the bottom right) is to pay attention to each form's curvature individually, in the direction of the intersection itself - so for example, a sphere is curving in every direction, whereas a cylinder curves only in one. Figuring out exactly which direction is relevant to us can help us, because at the end of the day the intersection line is going to be some manner of transition from one of these curves, to the other, and sometimes back to the first. This won't tell us exactly what the correct intersection will be, but it helps give us pieces to the puzzle, something to work with.

Continuing onto your object constructions, the patience and care you've demonstrated here as you've worked through each of these is phenomenal. This lesson is intended to be something of an important turning point. Up til now, we haven't really dealt too much with precision, and the organic subject matter of the last 3 lessons have definitely been much more forgiving - asking for relationships between forms to be defined specifically, but not always demanding that we figure out exactly where everything should go. This lesson definitely changes that.

By precision, I'm not talking about accuracy. Where accuracy speaks of the relationship between the marks you make, and where you intended for them to fall, precision speaks more to the way in which your intent is developed. When we lay down the start and end point for a straight line, that's a step that increases our precision, because we're thinking about the specific mark we want to make - not whether or not we've been able to achieve it. Similarly, the incredibly careful and fastidious use of subdivision you've used here, to pin down the specific location of every feature - ensuring that you never rely on leaps of logic that exist only in your head, but rather planning it all out and making your intent specifically known on the page - amounts to an extreme level of precision that I am overjoyed to see.

The thing about precision is that it forces us to think through our choices, rather than relying on a more general sense of whimsy or on arbitrary happenstance as to how closely we achieve our goals. The more precise we are here, it becomes almost inevitable that we'll also match it with accuracy - especially when we leverage the tools we're allowed to use (such as rulers). With all of this, you've done a fantastic job.

You also haven't limited yourself to especially simple subject matter - you've done a great job of leveraging a lot of unique curves as well, beyond just the rounded corners on some (which honestly would have been perfectly adequate). The way in which you've pinned down the curves in this one is something I find especially impressive, as you've done a great job of establishing them as part of a solid, three dimensional structure, rather than just as a vague swoop on a page.

That said, it is worth calling out that I noticed some sloppiness (or more accurately missed opportunity for greater precision) in the planning and execution of the ellipses on that same object, as shown here. In the orthographic top view, you defined the top/left/right edges of the square enclosing each circle, but not the bottom edge. Then, in your actual construction, you didn't draw the ellipses such that they touched each defined edge (resulting in a looser relationship between phases of construction, and a dip in precision).

One thing that can help with cases like this, aside from going through the steps to ensure that level of precision is maintained, is to remember what the minor axis line itself aligns to, when jumping between the 2D space of the ellipse, and the 3D space of the circle it represents. As explained here back in Lesson 1, we know that the minor axis (in two dimensions) aligns to the normal vector (in three dimensions) - the normal vector being the line in 3D space which sits perfectly perpendicular to a surface.

Actually, I have to stop myself here for a moment - based on your 3D construction, I interpreted that boxy block as having a top that was somewhat slanted, rather than horizontal and flat, so I drew my intended minor axes as lines that were slanting to match. This may have been incorrect, looking at the orthographics, but let's just pretend for a moment that my misinterpretation was correct, as it helps to convey the usefulness of using the minor axis lines here. If we can establish a vector/line that runs perpendicular to the given surface, we can produce minor axis lines for our ellipses to align to. That way, we're given something more concrete to match up with, rather than drawing any old ellipse that'll fit within the plane we've defined.

Anyway, so your work isn't perfect - but one case of skipping a step or two in the context of everything you've done throughout this lesson really isn't of concern. I'm still extremely happy with your work, and the good habits you've demonstrated here. So! I'll go ahead and mark this lesson as complete. Keep up the great work.