In fact, it's very similar to and old X11 game named "XBattle" I used to play. ftp://ftp.gwdg.de/pub/x11/x.org/R5contrib/xbattle-4.0.README
XBattle has many, many parameters you can tune (growth rate of "armies", decay rates, as well as persistent movement on production, etc.) All of these can be combined in different ways to get some really great game variants.