Final Fantasy Tactics.
I've dumped innumerable hours into thisgame in all its facets, completed (to my knowledge) the first ever SSCC
[that's Solo Straight Character Challenge; i.e. beating the game with the main character Ramza ONLY while allowing
him to use the skills from only a single class the entire game], and semi-regularly participate in VS battles against
others in my particular group.
Create a set of rules the battle will be set under. We play on actual maps within the game (sometimes we can do ones
that battles never normally take place on, such as ones shown in cutscenes), keeping track of terrain and character
locations with a terrain map. Since everything in FFT is calculated through very exact formulae, aside a very simple
1...100 RNG, carrying out these battles is actually not terribly complicated. 8)