Did some more SaVi development, finally discarding the X-only fisheye plot code in favour of reworked code that uses the Tk canvas widget throughout instead. In the process, the executable shrank by about 20%, too; I don't think the X libraries will be missed.
By not requiring X, SaVi is finally properly useful on Cygwin and with its weird Insight Tcl. So proper Mac OS X support can't be too far away, either, surely? But given that I've been using Cygwin for a couple of years and have only just gotten around to sorting out obvious niggles with Cygwin, don't hold your breath. I don't even use a Mac.
Had another query about the details of a rosette constellation; another subtle fix to a simulation got done. Getting phase offsets right between satellites' orbital planes can be quite tricky, and it's taken me a while to grasp how the constellations map onto the simulator. When the constellation has a lot of visible satellites like Galileo, it's hard to figure out from inspection what's right.
I'd be playing snowboarding games instead of typing this, but the family is watching television... the way to be productive in life seems to be to spend all the time you'd spend watching television staring at a computer screen instead.