Great arena idea, the game should be fun mulitiplayer, I would like to test it with humans some day, the computer players are abit predictable, mabe you could write an ai for it.
All players have the same starting position and the same chance of winning the scenario.
I like the concept of destroying the enemys castle, its sortof like a king of the hill, as each player guards the entrance to their castle.
Map Design: 1
You can't realy judge this on the map design, it could be better but its realy just a bunch of walls, mabe you could make the map slightly more intersting, flags, different terains, elivations up to the castles?
This has no story or instructions, mabe you could make some instructions so it is clear of the objective.
Thanks for showing us this, it could do with improvements, I would like to see a v2, I enjoyed playing this and noticed, mabe when a malitia is spwaned it could be tasked to move off the square so the next one can come, it gives human players a disadvantage otherewise. Mabe you could add other units, that you could get less frequently, archers, cavalry?