I've asked about the concept here as well: http://forums.xkcd.com/viewtopic.php?f=18&t=109979 http://forums.xkcd.com/viewtopic.php?f=18&t=109979 I suggested a t

I've asked about the concept here as well: http://forums.xkcd.com/viewtopic.php?f=18&t=109979 http://forums.xkcd.com/viewtopic.php?f=18&t=109979 I suggested a two designs and the one I mentioned on hn has an ascii drawing about halfway down the page.