Rithmomachy
en.wikipedia.org
en.wikipedia.org
A Windows Shareware version: http://www.stargraphics.com/ambush.htm
An Android version: http://www.stargraphics.com/amband.htm
http://www-pgss.mcs.cmu.edu/Publications/Volume18/Rhythmomac...
Nothing much mentioned about sudden decline in its popularity.
I guess, Games that are tied with the tradition of a culture tend to have a longer lifetime.
More important is probably its educational use in teaching Boethian arithmetic in the medieval university. By 1600, Europe has rediscovered scores of classical texts and was on the verge of making very major strides in mathematics. It probably just didn't seem relevant.