[MWForum]Erasing turtle lines

[Karen Randall]

I have a student working on an animation where it would be rather 
useful to freeze the background, then have a turtle drawing on top of 
the frozen background.  That would allow the turtle lines to be 
erased without messing up the setting.   As far as we can tell, MW 
doesn't allow for that kind of layering.

Using changing turtle shapes for the drawing/erasing doesn't give 
enough flexibility in what the turtle drawing is doing.

  Our solution so far is to have the background a solid color, then 
erase the turtle's lines after they are drawn by giving the same 
turtle commands with the pen set to the background color.  Since it 
would be nice to have a scene as the background instead of a plain 
color, I'm wondering if there really is a way that background 
freezing can be made to help, or if you have any other suggestions.

Thanks,
Karen