I just finished my sophomore year as an electrical engineering major. Now I've got a summer free (well, I work until 4:30), and I'd like to use it to self study something (one or more topics). So far, I've taken Calculus 1-3 as well as an ordinary differential equations course. I've taken two courses in circuits (one which primarily focused on signals), two courses in digital design, and an introductory mechanics and an introductory E&M physics course. I was thinking I could study something math-related that would be useful to me down the road. Something like PDEs or Complex Analysis. My second thought was to get a head start on some electromagnetism, but I don't want that to be a waste of time since I'll be taking a course on it anyway. Any good suggestions as to things that would be helpful for me to learn over the summer? I'm open to things useful to a wide variety of EE areas or related areas of science and math. Emphasis on things important to EE, but perhaps there's something interesting out there that's not particularly helpful, but is still interesting.