这里面有很多好东西！
http://canadaonline.about.com/cs/geosketchpad/index.htm
http://canadaonline.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fwww15.addr.com%2F%7Edscher%2F
qiutopia {learn and let learn}
qiutopia {learn and let learn}
真是好资料。谢谢了。