Tofu will be looking at your revisions, but I wanted to quickly address your question about the intersections. It's entirely normal for students at this stage to figure out how they intersect, and it is entirely normal for those intersections to be incorrect. At this stage in the course are merely asking students to give it their best shot, even if it's entirely wrong. This effectively plants a seed in the student's mind, which then - as they work through Lessons 3-5 - gradually develops as you're forced to work through the combination of different forms in 3D space (albeit in much simpler circumstances). Then we assign the exercise again in Lesson 6, at which point we talk about it a little more, since the student's in a better position to actually understand any suggestions or adjustments we may have to offer.