Added a root.update to help with OS X Tk problems. See <http://mail.python.org/pipermail/tkinter-discuss/2013-January/003343.html> (and the rest of that thread) and <http://code.activestate.com/lists/tcl-mac/1548/>. The side effect is that the simulation stops if you click on a menu.

Also, increased size of cyan text for distances.