Generates heatmaps for complex-valued functions, with redness proportional to the real part and blueness proportional to the imaginary part at each point.

Historical context: I think this is another one of my very oldest programs, along with the atombuilder, although the last modified date for this file on my computer is 02/03/2013 (I think because I went back and updated it at some point; you can still see the old code, which was just a sequence of statements and not organised into functions, etc., commented out at the bottom of the file).