That's nice, Martin --
reminds me of a Cloze engine I made once in the olden PLATO days -- you typed in your passage and then could ask for any distance between blanks, at what point in the text the Cloze stuff began, whether or not hints were given, and in what form, scored the thing and did some statistics with the class responses. And the whole thing interacted with stats and scores from a "guess the next letter" thing that used Shannon-Weaver stuff to plot the chances of the next letter being guessed, and with another exercise that used Osgood semantic diferentials,and I plotted the whole thing's scores in polar and in regular graphs...Sigh, them were the very old days. (And no one gave me any funds to do it - in fact,the administration was annoyed to see a Humanities faculty member messing about with computers)