A whole day playing with the Java 2D Graphics facilities for image compositing. It seems that Java does everything I need nowadays - in the 10 years or so since I first conceived this language, students have struggled to do this stuff at interactive speeds, and I've published research papers based on less technical progress than I have made today. Won't be able to do exactly the same stuff on Android, but let's cross that bridge when I come to it.
Further good news is that I haven't yet suffered the curse of working at home. When announcing this blog to a few friends, I mentioned my mental image of what happened to Dilbert. Quentin picked this up via Facebook, bringing the question of why monkeys don't grow beards to a new generation of readers.
 Blackwell, A.F. and Wallach, H. (2002). Diagrammatic integration of abstract operations into software work contexts. In M. Hegarty, B. Meyer and N.H.Narayanan (Eds.), Diagrammatic Representation and Inference, Springer-Verlag, pp. 191-205.