It uses Tkinter, but I will rewrite it in some other GUI toolkit if necessary. I'd rather avoid doing that, but since the GUI code is probably only about 20 lines, I suppose I could do that.

For instance, BeeWare’s Kivy lets you create cross-platform GUI apps in Python that run not only on all the major OS platforms but also on the web. But here we’ll focus on Briefcase, which can ...