[b]nice one![/b] concord
i was at http://engineering.concord.org/ht.html

is it possible to examine the source codes? That will be a new level of learning that Ejs currently affords.

For ur consideration:
in terms of instructional design, u may want add to the "r" and "t" keyboards, i think i was like stunned for a while, like most beginning learners trying to figure out how to use the applets.
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1379.0;attach=1620[/img]"play" and [img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1379.0;attach=1621[/img]"reset" seems suitable cos I am used to media players mental models.

even without words, it has meaning
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1379.0;attach=1620[/img] [img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1379.0;attach=1621[/img]