Note: this page runs completely locally in your browser with javascript (which must, of course, be enabled). Nothing gets submitted back to the server.
Note to users of old netscape: if numbers do not appear at the same distance from the center, you have to tell netscape to use fixed fonts for the text fields (don't ask me how!). Netscape 4 and older does not understand CSS and I'm using a hack to pad the numbers with spaces, which only works when the space character is of the same width as the numbers.
OK, enough of introduction. Enjoy the trainer!
Sergey Berezin / berezin at stanford dot edu