I have create a simulation according to your requirement above.
I hope it is what you want. Enjoy it!

translate strings in simulation to different language format before download
Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
Download EJS jar file(1400.4kB):double click downloaded file to run it. (18 times by 4 users) , Download EJS source View EJS source