A little sketch that colours the triangle red if the mouse is inside it. I'm working towards something I promise! :) The concept taken from the "Same Side Technique" example on this site where the formula is explained in detail:
Messing around with Processing and thought a manipulator handle widget might be handy to have for future sketches. So here's a real basic one. I plan to add arrows and make it less boxy but it does the job for now.