Stupid realization of the day: Floats in CSS potentially span several elements, depending on whether they need to or not. At first I found this weird, but upon further pondering it made perfect sense. You see, that's the behavior you'd expect most of the time. Want it to keep its place within the containing element?
clear to the rescue.
Drawing overlapping vectors sucks. I can't find a suitable way to do it! Currently, I use curly braces to mark sections along the line, but this is far from optimal. Especially with more than two overlapping vectors.