I’m going with the theme and switching from ImpactJS to Perlinspiel for my engine.  I saw Prof. Moriarty’s presentation a couple of GDCs ago and his engine always interested me.  Here are the links for anyone interested:

Main Engine Site: http://www.perlenspiel.org/
GDC 2012 presentation: http://www.gdcvault.com/play/1015620/Lehr-und-Kunst-mit

Neuron Fire