Remixed from technoboy10's demo to provide a crude solution to the challenge. (Needs a little work on the end cases, it was a quick hack)
First we draw a 10-line pattern, then we go over it again, a pair of lines at a time (one red, one blue), drawing only the segment starting from the last intersection point to this one. Calculating the X and Y of the intersections is one expression each - see the source code.
