change the order of proficiency symbols on the Progress tab legend
Rather than order the proficiency symbols alphabetically (Introduced, Mastered, Needs More, and Practiced), it makes better sense to me to order them by level of proficiency (which I assume is Introduced, Practiced, Needs More, and finally Mastered).
Great site by the way. :)

It’s actually not ordered alphabetically, it’s ordered by progression. The progression for “masterable” lessons is introduced, mastered, needs more. For ongoing, it’s practiced, needs more. This will make more sense, and be customizable soon when we deliver the ability to customize those proficiency scales. Stay tuned!