I don't know the answer to the following question, but it would be fun to come up with one. "Mathematicians turn coffee into theorems." -- unknown ?? I drink a lot of coffee, but when I shuffle papers on my desk, the coffee cup turns over & spills coffee all over the papers. Therefore, I'd love a cup design that is strongly resistant to turning over. This implies that the base should be larger than the top, and that the center of gravity -- even when full of coffee -- is very low. I also don't have a lot of room for storing coffee cups, so I'd still like them to _stack_ in such a way that they _nest_ & therefore don't occupy as much volume when stored. Finally, being a human, I'd still like to have a handle through which a finger could fit. The handle needn't touch in two places, so topologically it could be simply-connected. I envision some sort of "star-like" shape which will nest when the second cup is rotated 2pi/N. Like I said, I don't have a candidate shape.