My question concerns the demonstration entitled Coupler Curves of a Four-Bar Linkage by Eric Mahieu. In the enclosed code I have indicated my changes in red and additions in blue. The green dot represents the point being plotted. The extension value of -1 (minus one) determines Its position on the coupler linkage. I would like to move the point above (and off) the linkage by i.e. a Y value of an additional 1 unit. I suspect that an offset would be required but have been unable to make it work. How would it be accomplished? Thank you for your help. Dave F.