ok, this thing is something small I whipped up at school. Up until now I could never really figure out the best way to store mouse coordinates correctly, until someone mentioned arrays.
it works by storing the mouse coordinates in 2 arrays, then it just replaces the first entry of each per frame, and removes the last, then a line is drawn. 1 line per 2 entrys, to make the fading effects work.
in this version, I added a thickness button just for haha’s 
[swf=http://www.avalon-rev.dk/junk/kirupa/linerestriction_04.swf]height=400 width=500[/swf]
edit
I’ll have the source up soon, I forgot it at school :sure: of course I only got the swf file home with me (??)