not at all! I just recode it ,and it may be more clear for reuse!

I've solved your question and update the answer there http://www.greenfoot.org/scenarios/5747 。 help yourself please！

I've maken a improved version of this(http://www.greenfoot.org/scenarios/5769), may be useful under any situations

In fact the codes I’ve used are mostly from scenario CG2（http://www.greenfoot.org/scenarios/5740），you may find your answer there

I have just post a scenario to give you some tips.

very nice!

I can't understand the code refered to Trigonometric Transform , are there any materials about this ？

the “mini” mode looks lovely! ^_^

惠君老师又开讲座啦？^_^